My SD45 has been a drug addict for 25 years. My husband had pretty much disengaged except for occasional phone calls. Then 2 years ago, the dipshit walked in front of a train. Lost arm hand and one leg. Since then he has been killing himself trying to make her responsible and self sufficient. He helped her get a place, found someone to live with her to help at night and do some daytime HSSI hours.
Lasted about a month and she stared doing drugs and being nasty to the lady living there and having her street 'friends" staying and showering and evidently giving her drugs. It blew up a few times and he was had to go down when the woman couldn't take it anymore so he missed thanksgiving, finally came home had to go back then got home a couple of hours before the whole family was here for Christmas Eve. He was able to convince the helper to stay, but she wasn't doing much (can't blame her, she was getting screamed at constantly) and finally left for good. 
He went back down (she lives about 150 miles away.) stayed for a week, trying to get daughter to doctors for her psych meds, find a new person to live there, someone for daytime etc, stop doing drugs, get rid of loser friends. He had zero luck. He got a friend to stay for the weekend and came home.
Saturday night she calls, she got scared and called EMTs and was in the hospital and needed a ride home. He was going to go, 2.50 hour trip! I finally said NO! Tell her to call her mother who lives 10 minutes away. (Mother hasn't seen her once since the train accident) I don't know what she did, but managed to get home.
Monday he goes back, now she is having panic attacks, needs more meds, more doctors. Still no one is answering ad to live there. He is down there for 11 days. Nothing resolved, but she is on better meds, he has a few people interested in the day hours. Pays this guy to stay the weekend again so he can be here for Easter. drives home, walks  in the door and the guy calls and said daughter was doing drugs. He doesn't know who gave it to her as he wasn't home, he just wants to make sure husband knows it wasn't him supplying her. He agrees to stay the rest of the weekend and we have a nice easter with the grands.
This morning he packs up and goes back down, for god knows how long. I told him I don't care what he does as long as he doesn't try to move her to my house, but watching this and keeping my mouth shut has been hard. He is killing himself, I can see the stress on his face. He is shutting down, not laughing, not sleeping, takes little joy in the grands, his head is somewhere else all the time. I don't know what to do to help him. It makes me heartsick to watch him trying so hard to fix this asshole waste of space daughter. That's it, just a vent. No easy solutions.