There is a lot of info on this site. The first few things that maybe you should do:
1. Look at all accounts, if you want to stay in house, take her name off. Bank accounts, divide money and have own accounts. Make copies of all financial papers (taxes, her paystubs, medical if there are issues there, proof of any other issues). Keep copies in safe place outside of house.
2. Do not allow the kids to move out of the house. Have lawyer ready to go if she tries. BOTH of you have legal rights to children right now. Either one "can" take children elsewhere. You can get a temp
court order that children stay living in house and they are not pulled from current school.
3. You can use family court to deal with custody without going through a divorce. You can also have legal separation papers drawn up , you both sign them and file with the courts that has mostly everything a divorce has and then you are not legally responsible for her debt after separation.
4. Make sure any conversations are not in front of kids and kids are not even in house. If kids hear anything or ask questions, just say that these are adult things but that they have both parents who love them. At some point they may be interviewed through the courts, social worker, of social services. If they need it, you can look into family counseling. Interview person first to make sure they will work well for your situation.
Read, Read, Read.....if it comes down to making parenting plans come back and read again. If she talks to anyone that knows the family court system, she can file for custody and
child support pretty easily. So have everything ready to go, have talk , and have lawyer ready with paperwork to file next day if things do not go smoothly. Good luck! (We are not lawyers but have been through family court for more than 10 years...not fun, pretty, or fair.)