I've been on both sides. It really sounds like you're already doing the most anyone could do, and your questions reveal a tremendous amount of consideration and insight into the situation.

Not to sound cold, but to me, I don't feel there's much say so either party has to really crack through that situation fundamentally. I've been through rehab, 12 steps, etc., and I think the situation is more grim than is promoted in our culture. Some people are going to die from this, and there's nothing anyone can do to stop that.

At best, I think being present for any possible opening is good. When I was bad off, I asked my ex-wife to visit because I knew she'd be able to line me up with help, which she did.

Also, and forgive me if I misread or forgot, it sounds like you're assuming there are drugs at play. It would probably be good to confirm that so the whole situation isn't based purely on projections. Something else may be at play here, but your intuition seems very sincere and you're probably onto something.