I haven't been in your shoes exactly, but I can imagine how much I would love to help and support someone who is on a path for healing, esp someone I once loved dearly. I have that opportunity with my son now, but only because he is working a hard program voluntarily and we have that mother/son relationship. I struggle daily with my role and have to check my own behavior to make sure I am not stepping in a codie way.
That said I have l have let go of a few addicts, my ex husband and a boyfriend, after many failed efforts of believing I could help. The last time I saw my ex husband, after 8 years from our divorce, he came over needy and claiming sobriety and I spent an hour or so with him after he told me he needed gas money to get back home. I looked him in the eye and said, thank you for this night. I now realize I am no longer in love with you.
I didn't say that to hurt him, it was just a wake up for me. And I knew I could move on without letting him rent out a bunch of space in my heart and mind. I think it did hurt him, because he always depended on me to love him forever and he lost quite a bit of power in that revelation. I did give him $5 to drive home and he doesn't call me anymore.