sorry this has happened, and i do understand your pain and concern but you did ask him to leave you alone and you've decided to divorce him, still you go to him for whatever reason and decide you are gonna stop him from doing what he chooses to do with his life. kind of sound like a part of you still wants to be in control of what he does.
btw, i believe in the demon theory too. i was once that person who sought spiritual help and yes, i believe it worked for me. i've also seen that look in my ah's eyes twice and trust me, i honestly don't think it was him in control. i also think you put yourself in a very dangerous situation by trying to take his drugs. doing that is like a life of death deal for an active addict. "do what you gotta do but don't mess with the dope", kind of thing.
i know its hard and i know it hurts but you made a decision to let go, now its time to do it. its hard to let go and hang on at the same time.
you and him are in my prayers.