I am more worried about your mental health at the minute OP.
One line that stood out to me was about your 'only friend' getting higher rate PIP. You need to blank out what other people are doing and focus on yourself. Truthfully, are you feeling depressed? Maternity leave can be isolating, and with a young child, no money, and an unsupportive and frankly abusive DH you must be going through a lot at the minute. Your self esteem and confidence to me sounds like its gone through the floor.
You need to deal with yourself and how you feel, before you can find the strength to tackle this. Your situation is unmanageable, and your DH is being an arsehole. You are not lucky to live under his roof, he is lucky to have you there from the sounds of everything. If your child or a friend was being treated how your DH is being treated, what would you say to them?
You need to stand up for yourself, no one else will. But you are worth and deserve so much more than this. Not eating in the day, looking after a little one will make you ill.
First off, citizens advice. Google your local branch, go with your LO to a drop in appointment, take all your financial docs with you, as well as your creditors and they will instantly do a income and expenditure with you, so you can see the full picture. I worked for Nationwide in their credit card collections department, the CAB carried a lot of weight with us, and we were happier to help people who were taking proper debt advice, rather than ringing saying 'I'm skint'. It shows you are taking your debt seriously, and also shows if you have taken the trouble to go to them, you will maintain an arrangement. I have taken one pound a month payments on 20k of credit card debt before and frozen interest on the condition that communication was maintained, the pound payment was made every month on time, and that it would be upped as soon as that customer went back to work. It will be difficult but not impossible. There is light at the end of the tunnel you will get there.
But, by yourself. This dick you live with, is not providing you with emotional or financial support and quite frankly doesn't respect you at all. You will have to tell him the truth, but you are in the marital home, he cannot force you to leave without a court order, if he tries to force you out ring the police.
Speak to citizens advice, they will help in terms of benefits and help. Go on entitled to.co.uk - enter in your information with out your 'D'H and you will see how much better off you are.
Go talk to your GP as well or health visitor, you sound stressed and depressed, and I think that you might need some help there.
You must be feeling so isolated, but you aren't. I am happy to PM you and provide support if you feel you need it. I just wanted you to know it will get better, it wont be great straight away, but decisions need to made about your marriage, and then about your debt. Chin up.