DO NOTHING REGARDING THE HOUSE BEFORE YOU SPEAK TO A SOLICITOR
He cannot force you out, he cannot force a sale without a court order, he cannot walk away and decide how things are going to be.
YOU DO NOT HAVE TO DO WHAT HE SAYS.
Call a solicitor asap and make an appointment, explain the money situation and ask for a free consultation. It will be more affordable than you think.
Then get on to DWP and make a claim for Universal Credit and/or income support etc. It will take a few weeks for the money to come through but you can get an advance to see you through that period. If you were not entitled to child benefit when you were with him, you will be now so claim that too. At the same time, get onto CMS and claim child support. He has a responsibility to your child as much as you do and cannot be allowed to ignore that.
Then get a box and fill it with all the important stuff, bank statements, pay slips, baby's birth certificate, marriage cert etc. All the paperwork you can find and hide it, preferably at your sisters. Do the same again but with personal/sentimental things so MIL cant send him shopping for your stuff again, include jewellry and anything of worth. Again, store it at your sisters.
THen (Sorry!) look at how you can secure the house against him. You cant legally change the locks (although he may not know this yet) but you can add extra locks, you can add bolts to the doors. This is not illegal but it will stop him just coming in. Do you have a back gate you could add a lock to and you use the back door and keep the front door locked and bolted for example?
You need to get your boundaries firmly in place. HE left. He does not get to call the shots anymore. You need to get yourself a support team who will help you realise how outrageous his demands are. Do not answer calls from him, tell him you will only be communicating via text/email. When you receive one forward it to someone you trust (or post on here) and ask them if what he is saying is reasonable. This helped me a lot when my ex tried to continue the abuse from a distance. When you have lived with a bully, you lose all sense of what is ok and what isnt. I know this seems a lot to do but trust me, when you have done it you will feel safer. You will no longer be reliant on him for money, you will be able to relax regarding the house, you will feel protected against his bullying. Please, take it from one who has been there.
But I say again DO NOTHING REGARDING THE HOUSE UNTIL YOU HAVE HAD LEGAL ADVICE.
Take care lovey 