Answered your other post. We can't help someone unless they are willing to get help. They will only use us to get what they need so they can continue to use. We ten to put a pillow under their bottom, so they don't hit hard when they fall, they can always come home to us, you told the story of my son.
All I could do was pray for them. He got so bad, I had to kick him out and he had to go to the mission, I just couldn't have him in my home. I love him dearly, he is my son, but I didn't have to put up with his abuse. Not physical, but mental and emotional, and although he wouldn't realize it, spiritually too, it is the not caring that really hurts.
Al-Anon helps heals all those hurts. I am a recovering alcoholic and addict (prescription pills), have an on going eating disorder that I apply the 12 Steps to, along with my chronic pain. Just for today, I choose not to use. I am an adult child of an alcoholic and I found out I was codependent. The 12 Steps are applicable to all areas of my life. They take the focus off the people in my life, and put it on myself, and helps me to live my own life and let them live their own.
The thing I find that works is prayer. Put them in their God's Hands. It is not my job to play God and I needed to let go and let God.