Wow man. That is chaos and I'm sorry to read about it.
I agree with several comments here. You can't control it. She may not be allowed to be around the kids but the time she's around them while you're there sounds pretty bad with all the nuttiness going on.
Perhaps you should be calling the cops on her if you suspect there's a problem. They'll give her a breathalyzer and be done with it. It will also be on record which can only help you in court.
It sounds like it's time to work on a more permanent plan because the current state is not normal and neither you nor your kids should have to deal with this.
I wish you luck and I'll be thinking about you.