I'm not sure if this helps but here gos..... (drug/alcohol use mention ahead)
The summer of 2013 was the hardest 3 months of my life. My father, who has always been a drinker and who I knew was a pill abuser, turned to heroin. He lost job after job and every time it was "I dont know what happened! We just didn't get along! It didn't work out!" We staged an intervention and gave him a choice: go to rehab or leave the house. He chose, reluctantly, rehab. 30 days later he comes home. Supposedly clean. A week later he wrecks my sisters car and the police find open alcohol containers in the front seat. He was high and drunk. Luckily, not hurt.
July 4th 2013 my cousin is admitted to the hospital for a staph infection in her inside elbow. My mom goes to visit her. Begs with her, not you too. My cousin, 23, was always into the party scene. Late July I get woken up at 6am by a phone call, ironically my father, who tells me shes dead. She over dosed. She was drinking and her "boyfriend" shot her up and it was too much and she died. 23 years old, someone I grew up with, someone I thought I knew, someone I loved. I should have visited her in the hospital, should have invited her to my apartment more often, should have, should have, could have. You cannot take those moments back.
After a year, my family still healing, my aunt never the same again, and my dad is still on heroin. He tries to self detox. It never works. My parents are getting divorced. My dad would not get himself together so my mom didn't have a choice but to sell their house, split the money, and part ways. I don't know where he is right now, I think a few states away... He spent Thanksgiving at his friends house instead of with family. We exchange texts sometimes. I haven't seen him since the summer. I miss him.
You cannot force someone to get clean. Theres a saying, someone on heroin either winds up jail, rehab, or dead. A VERY small percentage get clean.
If it helps, I do have a positive story. A girl I went to high school with was best friends with my best friend. We didn't hang out often but my friend told me everything. The girl met a guy (this was a year after we graduated) who just got out of jail. She was his "only friend" and the "only" person he could rely on. His family wanted nothing to do with him because of his addiction. The girl wanted to date him, wanted him to love her, so she went and did heroin. Twice, but enough to get herself addicted. From the way she described it, detoxing felt like her bones were screaming and on fire.
She went to rehab and is now.... 3 or so years clean and sober.
I guess my point to all this is you cannot fix him and do not ever think you can. You can be there, be a supporter, cheer and root for him, but you cannot fix him. Only he can get himself past addiction. And it will be a LIFE LONG up hill battle.
Good luck, and if you ever need someone to talk to, feel free to PM me.