I'm sorry you're having such a tough time. I agree with the therapist idea with a plan on gradually finding alternative housing for him. If he continues to live with you maybe you could come up with rules or a plan so it's not so stressful to you. For example, while he lives with you the substance abuse has got to go. He is responsible for seeking treatment for this. I hope you make a decision that brings you peace. Sending big hugs.