RB, keep on going to Alanon.
You are NOT an idiot for wondering wtf he was doing when he was not home from a 7:30 meeting by 10:30! First of all, as you say, trust takes time to rebuild. Just b/c he SAYS he is doing so and so certainly doesn't mean it's true, based on past experiences, right?
Second, why the hell didn't he call you and tell you about this change in plans? Seems to me that would have been the responsible thing to do. So yeah, I wouldn't be so certain that just b/c he says he is not drinking, he really is not. This behavior is not right, to me.
Again, hang in w/Alanon and here. You are doing nothing wrong, and in your shoes, I would have felt exactly the same. It's hard, and while Alanon helps a lot, it surely doesn't end the pain.