This has to be the hardest when you're a parent and it's your son or daughter, my heart goes out to you.
My qualifier was my XRAH so I don't have a lot of experience but I do know this, I had to let him fall for him to recover (and I had to recover myself I was as sick as he with my enabling and codependency)....and I really thought he never would when I finally left him, it was only after DUI #2 and a myriad of other issues due to me not holding him up anymore that he hit bottom. It was something I wasn't expecting and that had nothing to do with me. I was watching an addiction show the other day and the lady helping the family let go of their child said even though they had to let go and live their lives that you never know what the future holds, she said and I quote "as long as they're still breathing there's hope they will choose recovery at some point, but until then you have to let them live their life and you live yours." That really touched me because it I thought it was a good example of healthy detachment....you detach not because you don't love them but because you don't want to love them to death.
I'm sorry you are going through this I know it's hard.