"She's toxic, and not fit to be a parent or my wife at this point."
Yeah I have to agree, based on all I've read about the situation. It's odd that she seemingly still wants to be in your company, and in the kids' company, when you all anger her so. Perhaps she is less certain of what she wants than she declares.
I am somewhat relieved to hear that B (along with L) seems to be supportive of your position. Maybe that's why W doesn't want a clean divorce, because then B would leave too and she'd end up alone.
Nasty, ugly, unpleasant situation. I don't envy you. Maybe if W hits bottom she'll get some help, and consider some meds after all. I imagine she'd have to hit pretty hard, though.