You need to leave.
The big picture might be too much right now, so just do one thing that will help you leave safely.
You don’t need to think about housing yet. You won’t be on the streets with your children, I guarantee you that.
First you need to let people who can keep you safe know you are leaving. You need to tell the police. Next time you leave the house without him go to the station in person and tell them everything. They will help you leave.
If you can’t do that then choose a day to leave, don’t pack bags unless you can 100% be certain he won’t find them. It needs to be like any other day, just walk out with the children. Literally everything else can be sorted out afterwards. You just need to go somewhere safe. Your parents, a friend, the police station.
I say this because men like him would rather see you all dead than let you leave. That includes your children. He won’t feel shame, he’ll feel righteous anger, before and after.
You are in a better position than many women to leave, your parents are “beside themselves” - they care and will protect your. Your BiL works in DV and will care and will signpost you to the best help.
Side note, The Dogs Trust freedom project will keep your dog safe until you can again.
You can do this. You need to.