- no need to rush into any child support payments. You know you're a good dad, you know you'll provide for them, you don't have to start paying her that child support now, let her move out and let her pay for her apartment and furnishings, etc. by herself.
- get a separation agreement in place before she moves out, you can agree to separation but don't agree to dissolution anytime soon.
I'm not sure about your specific location but where I live, once a separation agreement is in place, any debt that she accumulated after the separation agreement is in place is something that she will be responsible for, not you. Don't let her run up credit cards and burn away your savings until the separation agreement is in place - this is to protect you.
I guess your first step now is to see a lawyer determine what your options are and make sure you find a lawyer that isn't just there to help you sign papers, get one that's there for your best interests and won't fold and give her everything she wants.
How have you been holding up Tristan? I know you were stressed out something fierce the other day when you finally put your foot down.