What is your price?

I have noticed that when my girls come home from a weekend, or even an evening with their dad, they are more ornery, whiney, and more difficult to handle. I hit my boiling point today with them. Their dad brought them home at 830 this morning and Boston started in within minutes of being home.....Needless to say, that set the tone for the rest of the day. By 830 this evening I had had enough. I called their dad to find out what, if any, benefit he was to our children. He has yet to do anything to provide for them. He then told me that because of the "cute little ORS stunt" that I pulled that he didn't get the really amazing job that he interviewed for. Apparently, if you don't pay your child support it gets reported to your credit....who knew! So that is my fault......He then told me that if I took care of ORS that he would walk away from our girls. I wish I knew how to proceed from here. I want nothing more than to find an amazing man who wants to adopt my girls as his own. Someone who can show them what it means to be a dad and a husband! But how will their dad walking away from them affect them? I don't ever want them to resent me for the things that their dad has done. It really makes me sad for my girls that their dad has put a price tag on his love for them, though I'm not sure it really ever existed....