Glad that you've heard from him... I think that's one of the hardest things for "Mom" is just not knowing. He'll probably do just fine. When my hubby was in basic he always called telling me all the things he was doing wrong and everything the drill sgts said he would get kicked out for... he ended up getting his "ducks in a row" and graduated just fine.
I think the pressure and the worry over not getting it is part of the total package of preparing you for "whatever" after you graduate.
Good to hear he's doing well though!