About the initial mass of the universe, yep, correct. Given all of what we know about cosmology and astrophysics, a universe smaller than a certain size (the size implied by the current measurements of universal expansion) should never expand. Hence, a beginning moment is needed to “spark” the current expansion we observe.
This is known as cosmic inflation.
https://en.wikipedia.org/wiki/Inflation_(cosmology)
This flew in the face of the Static Model of the universe, which held sway from Ancient Greek times all the way to the 1950s. The Static Model supported the non-existence of God, because it destroyed the Kalam cosmological argument which implied the necessity for a Creator.
In short, Big Bang needed an unexplained period of inflation (which was an EXTREMELY brief period of time - a 32-position decimal fraction of one second), which needed an entity outside of the universe to initiate - an entity that we have known for millennia as God.
While I think you are right in that the Static Model contradicts the premises of the Kalam Cosmological argument, I have read that Aristotle at least used a form of the Contingency Cosmological Argument to conclude there were either "unmoved movers" or an "unmoved mover" beyond the Greek gods (who were themselves contigent, just vastly more powerful than mortals on his view).
Between the two, I find the Contingency Cosmological argument more convincing since the premises are easier to establish. But I may be biased, I had thought of this version of the argument before I had heard of it, although I had not developed and defended and clarified it as well as the great philosophers.
Still, I think the Kalam argument is easier to understand the deduction of so I like it better in that respect. And I think it may appeal to the irrational modern impulse to regard an argument as more sound if it uses recent scientific discovery in some way.
Might be that God did something like that, but scientists cannot explain it that way, because that is outside of the realm of science.
If we evaluate it as science, they simply fudged the numbers. It may be a more sophisticated fudge factor than a high school student trying to fake the results of his science project that didn’t turn out the way he expected, but it is no different in spirit.