I'll chime in on this, to relieve Nereid from the duty of having to keep explaining to you all by herself how science works-- it's a daunting task! Let me just tell you that you keep stumbling over a fundamental misconception about what science is for. I don't blame you for this misconception, it is reinforced constantly by sloppy science writing, but the fact is that it gets a quite unwieldy for every science publication to keep having to repeat what I am about to tell you.

The purpose of scientific theory, like the Big Bang, is not to tell us what "really exists", what "really happened", or what is "the real reason" things behave they way they do. That would be way, way too difficult, and frankly, we have no way to test such claims. So your continual criticism of the Big Bang based on the fact that it cannot tell us what "really happened" is not actually a criticism of that theory at all-- it is a fundamental misunderstanding about what scientific theory is capable of.

What a scientific theory is capable of, and what the Big Bang theory is a wonderful example of, is organizing, unifying, and predicting observations. In effect, a scientific theory is nothing but a kind of shorthand that can be used in place of a vast body of experimental data, most of which is entirely hypothetical because we simply haven't bothered to observe everything we possibly can (take the Hubble deep field, for example, and ask-- how many other deep fields are there that Hubble did not look at?). To the extent that the observations that haven't been done yet also conform to the theory, we say the theory is predictive (an aspect that is only testable in hindsight, when we actually do the observations), and to the extent that the theory unifies and makes sense of existing data, we say it is explanatory.

But either way, at no time does the theory ever cut loose from the body of existing and potential future data, and become what "really is". It just doesn't. I'm sorry that things you have read somehow led you to believe otherwise, but there simply is no valid criticism of the Big Bang that sounds like "but how do you know it is really right?" Thus to answer your question above, what separates the BBT from the "swiss cheese theory" of the Moon has nothing to do with which is "right or wrong", it has to do with which one unifies, organizes, and simplifies our understanding of a wide body of existing data and points to intelligent choices for new observations, and which one does none of those things. Do you see now?

Scientific writing does not make this clear at every opportunity, but it is just an implicit aspect of the entire process that bears repeating every now and again.