You know, they say you can see the relapse before it actually happens.I can't guarantee you that he is going to use, but from what you are saying and your suspicions, it looks like he is not doing well. When my daughter relapsed, I could see all that old behavior coming back before it happened.
What it taught me was that my gut feeling is right,if i think someone is using, I'm probably right.I know waht sobriety looks and sounds like and I know what addiction and all that craziness looks like too.
I go to alanon and it really helps me..do you go?