How was BT and AIT if you wore glasses? How were you trained with astigmatism?

Shooting with an astigmatism is, fundamentally, no different than shooting without one. I went through most of my time in service without even knowing I had one. Just pay attention when the Drills are talking about sight picture and you'll be fine. Looks like your other questions were already answered.

Also, pro tip, wipe your glasses down with shaving cream before you go to the range. It'll keep them from fogging up while you're qualifying on your rifle.

Yes you get an eye exam at boot camp. Yes you get issued glasses. No you can't wear your civilian glasses. I personally don't know how to train for shooting with astigmatism. I shoot with glasses and the primary issue is making sure your glasses are in the exact spot they are supposed to be for optimal vision. If your glasses break you get new ones. If your boot camp glasses break, they get you new ones. But good luck though, those things are mighty durable. I still have mine. Scratches galore on it, but still in one piece.

Your glasses should be the least of your worries man, keep your mouth shut and your eyes and ears open and you will do fine.