I think the first thing, Ottawa, is to be patient and just listen to him. It sounds like you have already. So that's a plus. However, don't push him into talking about issues he isn't ready to.
I also think just being there as a support system for him is VERY important, because you may be the only person he trusts and he has for support.
Don't push him into therapy if he doesn't want to or isn't ready yet.
Wow. It sounds like he went through something horrific.
Just be reassuring, nonjudgmental, and help him in anyway that he asks.
I hope this sounds ok and helps a little.