If, between you, your savings are less than £16,000, you'll be entitled to some Universal Credit. Make a claim the day after he gets his final payment from work.
On your income alone, and assuming total savings are under £6,000, I reckon you should be entitled to £400-500 month. This money can go to pay the bills.
If he has savings, or gets redundancy, he should use that money to pay down any cards etc that he has, which will reduce his outgoings. (Actually, if his credit's good he could do a balance transfer to a 0% card, which would mean that his repayments are actually reducing the debt, not just covering interest.)
Why aren't you getting any maintenance from your child's father? He has a responsibility here and it sounds like he's not meeting it. Start the process of getting some money off him!
Overall though, I think YABU. He's been subsidising you and your child and now his financial position has changed, you don't want to do the same for him. I'm afraid your posts have a slight undertone of your DP being a meal ticket.