I agree with the other comments that it would be best if you were NOT at the house when he comes over to do his work. It's too easy for him to slip back into the "we" mode, which is definitely not what you want to hear.
Is there some other way he can contribute toward child support besides working in your house? I realize he can't get a job, but perhaps he can make some products that you can sell for cash on eBay? Or perhaps he can offer services on Craig's List and have the customer pay the money to you for his services? Just some thoughts.
Hang in there. Life after divorce gets much better once you get him completely out of your life so that you can move on and create a much better life for yourself.
