Dear Nicole:
I second the Exit Strategy advice.
He needs psychotherapy and probably, he also needs to stop smoking pot. I heard a long time ago that pot, unlike other drugs, is harmless. But I read so much about how it harms people, individual stories (not told by an agency, let’s say, trying to convince people this way or that). Often, I read of anxiety being significantly increased following pot use. And anxiety is the core issue of most mental disorders.
So he needs help, competent, professional help, that is. The only help you can provide him is to make appointments for him to see competent professionals. Without him attending the appointments and following through with the work required, an exit strategy is well, the only reasonable choice, as far as I can see.
anita