You really are a fighter, Maggie. Hold on to that - it will get you through.
You are going through such a lot and you have such genuine worries for the welfare of your family. When I read your posts, I see two different issues. One is how you and your children can be happy and secure, emotionally and financially. The other is whether your relationship with your A will continue.
The sad fact is that financially you tied yourself to someone who isn't very responsible. So through no fault of yours, you have to pay some of the price for his irresponsibility. It seems to me that this is your most urgent problem to solve. You are a smart woman and you have told us that you have some resources to help you get employment. Your A needs to sink a bit lower before he is ready to quit. So please think about rescuing you and your children before the finances get worse. Is there a debt advice centre who can help you separate yourself financially from him?