Daughter's boyfriend has a very toxic home and I don't want her at his house because of it.

So I need some advice, opinions or just maybe even to be reassured that I'm doing the right thing. My daughter who is 17 is dating a guy who is 18. They've known each other since middle school. He's a terrific kid (good student with aspirations of going to med school) and gets along with me and her younger sister as if he was part of the family.The problem I'm having is with his parents. They both seem to have a serious problem with alcohol. His father is working on about his 6th DWI (he has to blow into a breathalyzer in order for his car to start) and his mother gets black out drunk and then screams and yells and puts him down by saying awful things to him several times a week.She has drunk texted me in the middle of the night several times lately saying Me or my daughter are trying to steal her son from her. A couple weeks ago she drunk texted my daughter at 2am talking a lot of crap about me, that was the coherent stuff anyways. These texts are usually followed up by texts from the boyfriend profusely apologizing for anything his mother may have said while drunk.Now it's gotten so bad that when he comes over she's calling him non stop to complain about how awful I am and that I'm trying to take him away from her, last time calling once crying claiming to be depressed and needing him home. She was drunk. The reason she dislikes me so much...is because I won't allow my daughter to go to their house or out to dinner with them. I had to put a stop to it because of the toxic nature of the household and a drinking and driving incident that happened with the mother driving him and a friend of his somewhere. She got rip roaring drunk once recently and screamed some horrible things about my daughter, which she heard. I tried to just come up with reasons for her not to be able to over there when invited but she kept pushing and accusing me of trying to set her son up, whatever the hell that meant so I finally told her straight up what my concerns about her going over there are. Now I'm the devil and she's making mine and her son's life hell (his more so than mine obviously).So she now has decided that I'm a danger to her son and he can't come over anymore (no fucking clue why other than spite) but her son wants to be at our house all the time because he's so depressed and miserable at home. She uses the phone tracker to find him at my home but he's 18 fucking years old. It's very Norma Bates.I just don't know how else to handle this. We want him around but not at the expense of my peace. Thoughts? via /r/Parenting http://ift.tt/2wrLLgA