"I'm grateful that they are paying.... But sort of feel like we are rescuing him. I don't want to be homeless. I don't want my daughters to be homeless .."
I do understand, however, his parents are enabling both of you, keeping you both stuck.
There are things that you can do to stop the bleeding, to plan for your childrens future. My gut tells me that this won't be the last time you will be in arrears on your bills.
What are your bounderies with him? What are your plans to improve the situation for you and your children, to keep a roof over their head?
Ask yourself the hard questions, where do you want to be in 5 years...and...how are you going to get there?
I know this is not easy, however, if you do not have a plan...you plan to fail. Please continue to work on you, read all of the stickeys and cynical one's blogs, very helpful information at your fingertips.