From *my* limited understanding about physics, I have to say : Is any of this, about time and everything, actually true?
Can you be a little more specific about what you mean by "any of this, about time and everything"?
We have a very good cosmological model, the big bang, which predicts, for instance, the proportions of hydrogen to helium (and other elements) in the universe, and that prediction has been shown to be very accurate.
There were some issues with it, for instance the smoothness of the universe from regions that were outside of each other's light cone and thus didn't have time to interact. Inflation has given us a good explanation that can deal with some of those problems.
Based on our current understanding it's possible to build consistent models in which there is no time before the big bang. But there are other models, also consistent with what we know, in which there
is a time before the big bang.
The real issue is that we don't yet have a theory of quantum gravity (though there is a lot of work being done and real interesting breakthroughs being made), and our current theories simply break down at t=0. We need better theories to get beyond our current understanding.
So, we know a lot about cosmology, but there is a lot that we don't know, and this includes
whether or not the question "what happened before t=0" is a meaningful question. It's entirely possible that it's not, but it's also possible that it is, based on current physics and cosmology.
This is cosmology, the exact inverse of QM (at least in terms of magnitude). Is it actually supposed to provide explanations, as far as time for instance, or is this also only about math and predictions (but not explanations as such)?
Physics and cosmology can provide answers to specific questions. Whether or not those are "explanations" is a more philosophical question, I suppose.
QM certainly does apply to cosmology by the way. For instance the slight density variations that became galaxies were originally quantum fluctuations.