I'm not sure if I can anything but support, which you certainly have. My situations a lot different an my children are grown.
The points about the cocaine seem good to me. She has crossed into something much more serious from a legal point of view. Is there anywhere you could go to like your parents while you get your head together? Don't make a big deal out of it, just pack up some stuff and get out of town for a while.
I really feel for you but the situation is now about your son and what's best for him.
Best of luck with this awful mess.