J.B.
What an awful spot to be in. I think you are seeing the obvious now, that your mother is cruel and abusive and a lifetime of that probably contributed to you being attractive to a husband who is also cruel and abusive. Abusive people sense vulnerability and move on it like prey.
You should be able to get temporary orders for child support an possibly spousal support (if there is a big enough difference in pay between you and your husband) right now. You don't have to wait for the divorce to be final - there are guidelines in your state for how much he should be paying you. Find those online, run the calculations, and see if that plus your paycheck are enough to get a small place for you, your son and the baby. See if you qualify for any sort of public assistance
As much as this sucks, you're going to have to stand on your own two feet and not rely on your abusive mother and husband. You have to break free of them. You can do this - it will be hard, but you can.