When the bill collectors call I would tell them the truth. Tell them you are supporting 3 children on your own, and that he has a job. Let them know he has an apartment and give them the address and phone number.
I know it's sometimes tough to deal with teenagers under any circumstances. She is old enough to understand that you are going through a rough time too.
I have to agree with wants out about not tolerating disrepect or name calling. When my son was around that age he started behaving like that. I literally cleaned his room of everything. Left him his bed, dresser and clothes. I made him earn the luxeries back one by one with good behavior.
Out of curiosity, are your children doing individual counseling or is it family counseling? Are you able to have counseling directly with you and your daughter to solve your conflicts.
I am sorry you are having such a bad day. I hope tomorrow is better.