Haven't read all responses, but you basically described my parents and me when I was young. :-) Same dynamics, but my dad was in another state so visits were farther in between and longer. I even asked to move in with him when I was 14 and my mom said "ph hell no!" bc she knew he wouldn't be responsible to keep me out of trouble.
It took me years to see through all of it and realize that my mom was doing the much harder job of laying down the law and protecting me. There are LOTS of times she kept me from getting myself into major unhealthy and dangerous situations and I'm so thankful she had the guts to "be the bad guy" for all those years.
Hang in there. :-) I'm not sure what to say about how to keep your heart from breaking as she sorts it all out. :-(. But she needs you to stay strong and do what's best for her even when she hates you for it.
And now I'm going to go say thanks to my mom, too. ;-)