Expansion of the universe No I understand the BBT. But it doesn't even try to explain where or how a universe creating singularity appeared in the first place. The main question the BBT presents. Also, there is no way yet of proving that bodies in space aren't actually just moving apart evenly, increasing the space, rather than assuming the space is expanding. It would look the same. I believe stars release space, space being composed of just radiation like light, which they generate by fusing matter. If all stars release space then space appears to expand. But if you'd prefer I believed a magical point in nowhere with enough heat and energy packed inside to spawn our universe just happened to happen, I say no thank you.
The other problem I have with it is the way physisists say "to ask what came before the big bang is a bad question", because time only exists once the ball is rolling. If nothing existed before this singularity, there would still be nothing now! It's a huge mess of a theory. Even Roger Penrose's idea on how it works is ridiculous and he's been trying to explain it for longer than I've been able to walk.
The CMB is the only good evidense for the Big Bang Theory. But I think it has a different cause. I don't know how or from where, but if its the only reason to believe something as invented and stupendous as the BB, I'd rather wait and see.
Finally, I think at least half the reason the BBT took off is because it fitted in so nicely with the bible. God spoke and shazam, a universe! Sounds like one and the same to me. Fiction.