You say "Until such time as they are shown to be invalid or inapplicable to empirically verifiable characteristics of our universe, they should be considered as justifying the conclusion that it is at least probable that the universe had a beginning." That's not really how it works. Science doesn't assume that a model is true until is is shown to be invalid. Science first needs to find lots of evidence for the model.

When you talk about the beginning of time, you are unwittingly contradicting yourself. You say, "Secondly, if the physical universe (and its physical time) did not exist prior to the beginning, then it was literally nothing." This statement is nonsense. You can't refer to what anything "was" before the beginning of time because the word "was" refers to some past moment in time. The statement is thus rendered meaningless.

"Fourthly, if nothing can’t do anything, then it certainly cannot create anything. Thus, when the universe was nothing, it could not have created itself (made itself into something) when it was nothing, because when it was nothing, it could only do nothing." Again, you are misusing words. "Nothing" isn't a thing. To say that the universe "came from nothing" doesn't mean "It was created by something that was nothing." It means "It wasn't created by anything." There is no contradiction in that. The contradiction only comes when you try to reify nothing.

"his transcendent (and independent) creative force beyond our universe (and its space-time asymmetry) is generally termed “a Creator.” " No, a "Creator" refers specifically to a sentient creative force. The Universe could easily have been created by something lifeless.

"Was the Big Bang the beginning of the universe? Many physicists think that it was because the Big Bang was the moment at which space-time came into existence and because there is no physical evidence for a period prior to the big bang."
This is factually incorrect. Whether the Big Bang was the beginning of everything is still heavily debated, but most physicists seem not to think that it was. All physicists know that we cannot trace the evolution of the Universe back in time before the Planck epoch without a complete theory of gravity, and thus we do not know what happened at that moment. Also, the Big Bang theory only says that the Universe was once in an extremely hot, dense state before expanding and cooling. The only way that the Big Bang theory says anything about a point in time when the Universe began is if you blindly follow the predictions of general relativity without accounting for quantum effects, even though physicists know that quantum effects must be accounted for during this early period.

The rest of this section is just a big misunderstanding of modern cosmology. First of all, none of the geometric proofs apply to what you are referring to as "quantum cosmology". That's because you are referring to theories in which the geometry of general relativity is not necessarily true on all scales. (For example, in loop quantum gravity, spacetime is discrete). While they still apply to some non-GR theories, their scope is not as broad as you imply.
These proofs also don't apply to a multiverse. That wouldn't make sense at all. They might prove that every universe within the multiverse had a beginning, but not that the entire multiverse itself did. The problem here is that you are confusing different meaning of the "multiverse". The theory of eternal inflation says that there are many different "bubble universes", but these are not actually separate universes. There is a path through spacetime connecting the different bubble universes - it's just impossible to traverse such a path at subluminal speeds. On the other hand, a true multiverse has completely separate universes, and none of these theorems apply to it.
Third - not a single one of these theorems actually says that time had a beginning. They say that there has to be a past singularity in any Universe that is always expanding. They say nothing about whether or not this singularity was the beginning of time, and thus cannot disprove models such as the "Big Bounce" or most versions of the cyclic Universe. They also can be resolved quite easily if the Universe was not always expanding (for example, the Big Bounce implies that the Universe was once contracting).
Fourth - a singularity is a point where our knowledge of physics breaks down. Any time we get a singularity in a calculation, what that means is that the model we are using to do the calculation is not quite accurate. Singularities are resolved by finding more descriptive models that can describe the conditions. The entire purpose of quantum gravity is to get rid of singularities so we can understand things that general relativity leaves us in the dark about. Any complete theory of quantum gravity will not have any singularities at all, and thus, the BVG and other singularity theorems cannot possibly apply to it.
Fifth, the two possible pre-Big Bang models you give are not the only possibilities.
Sixth, it is false to say, "even if there were multiple pre-Big-Bang eras, it is likely that these eras would have to have an expansion rate greater than zero." Most pre-Big Bang models say the exact opposite (again, the Big Bounce provides an example).
Seventh, you are wrong to imply that there are no possible models to get around these theorems. We just don't know what model is right yet. Physicists are not going to claim "We have gotten around the BVG theorem" until they prove that the correct model gets around it, not just that some models can. But, in our present state of knowledge, it is impossible to tell which, if any, of our current models is correct.

I can tell you for a fact that the second law of thermodynamics puts absolutely no constraints whatsoever on how far back time can go. If you think it does, it's because you don't understand how the law actually works. The second law of thermodynamics is a statistical law, not an absolute one, and it is only true because the Universe is currently in an extremely low-entropy state, which was even lower in the past. There is no physical law that prohibits there from being some point in the past where entropy was actually increasing (in fact, before the Big Bang was discovered, this is exactly what physicists believed to be the case). With the discovery of the Big Bang, trying to use the 2nd law of thermodynamics is even sillier because there is no reason to assume that the entropy of whatever existed before the Big Bang was increasing, or that entropy was even a meaningful concept in this era.

Now on to the fine tuning section. First of all, right at the beginning you are holding physicists to a double-standard when you criticize them for postulating unobservable parallel universes and then postulate unobservable supernatural design in the same breath.
It should be noted as well that naturalists need not believe in the multiverse. We can remain completely agnostic about the cause of fine-tuning. It is only those who posit design that have to point to one of the many possible explanations and say "That one has to be the right one", even if there is no evidence for it over the other possibilities.

The low entropy of the early Universe indeed can't be explained as pure chance - in fact, the extremely low probability of entropy decreasing is the reason that the second law of thermodynamics holds true. It is not an absolute law - it's just ridiculously unlikely for it to ever be broken on reasonable time scales (though, of course, given enough time, it will be broken - this is where the concept of a Boltzman brain comes from).
Anthropic explanations also are not sufficient to explain it because the entropy is lower than it needs to be for life to exist.
Having ruled out anthropic explanations, the theist may want to claim victory, but the theistic explanation has the same problem as the anthropic one. A universe would not have to be designed with such low entropy for life to exist - thus design is not an explanation either.
The true explanation is likely a physical one that will be discovered as our understanding of physics, the early universe, and entropy, improves.

The other five constants can all be given an anthropic explanation if there is a multiverse or if these constants vary throughout the Universe. However, they could also be explained by simply pointing out that the constants don't actually need to be the way they are for intelligent observers to exist. What makes you assume that intelligent life has to be carbon-based and has to exist on Earth-like planets orbiting Earth-like stars. Even if you can't imagine how life could exist in a Universe that is vastly different from ours, it doesn't follow that life couldn't exist. Certainly, if someone just showed you all of the laws of our Universe (and you didn't know that they were the laws of our Universe), you would have no idea that these laws could produce life. The exact method by which life came about in our universe is very complicated and couldn't have been predicted beforehand - yet many think we can completely rule out the possibility of life in universes with different laws of physics just because no one can imagine how life would emerge.

The multiverse theory doesn't violate the principle of parsimony if the alternative is theism. The multiverse theory makes one assumption and one assumption only - multiple universes exist - and that assumption explains fine-tuning. In addition, that assumption isn't a particularly big one. We already know that at least one universe exists, so making the jump to more than one isn't very big. Compare this to assuming that God exists even though we know of nothing that is anything like God. It is quite natural to wonder if there are other universes. In fact, it would seem quite unnatural for there to be only one universe. This single, lone universe would be the ultimate cosmic outlier.
The idea that invoking an infinitude of objects automatically violates the principle of parsimony is pure nonsense, though even if it were true, invoking an infinite God would have to violate the principle just as much. The principle of parsimony is not about how many things you claim to exist (otherwise, we would already be in extreme violation of it by positing the existence of unimaginable numbers of atoms just to explain our observations). It is about how many assumptions you make, and how far-fetched these assumptions are. The multiverse hypothesis makes one, simple assumption, while the God hypothesis makes many complex assumptions (especially if we pick your particular version of it). If I am forced to choose between them, there is only one parsimonious decision.

Finally, the claim that the multiverse itself must be fine-tuned is simply wrong. Certain very specific versions of the multiverse hypothesis require fine-tuning to work, but in general, the multiverse doesn't require fine tuning. If you just have a bunch of universes with completely random laws of physics, you will eventually get some that support life. That's all you need.

"Many physicists believe that it is not, not only because of the above three problems, but also because of the likelihood of a Creator." Oh come on, we both know that that isn't true. Even if you believe in a creator, you don't get to project that view on to the entire scientific community. Many physicists do not believe in the multiverse, but this is because there isn't enough evidence, not because they think a creator is a better explanation. Most physicists don't even believe in a creator at all. It's maybe worth pointing out that the fine-tuning argument for the multiverse is often taken seriously by physicists and physics publication, but I have never seen a physics publication that takes the design explanation seriously. At best, it will be briefly mentioned that some people posit design as the explanation before moving on to more serious explanations.

And yes, I am fully aware that I just used the plot to Pinocchio as an analogy for my understanding of God's relationship to the world. :)