chasing I understand, especially in your case, that it is easy to blame the ILs. They are, evidently, twats. But if your DP was in any way decent he would treat you well in front of his toxic family. As it is, he uses the opportunity to treat you worse. Like a bully, he uses his family as a back up, cheering him on. MN can be very much leave the bastard, and it can be very overwhelming for some who come for advice. I rarely get involved in relationships threads here, but you're one of the quiche. Leave the fucking bastard.
I'd shout it, but it wouldn't help would it? Right now, and I don't mean to be condescending, or whatever, but I would guess you are in the stage where you are looking for reasons to stay. He's a great dad blah blah. Once he let you sleep on the sofa while he did the night shift. But anyone who plays the game of giving you reasons to stay is not helping you. No-one in this quiche wants you to be anything other than happy and SAFE.
We can't force you to leave, but I think I speak for everyone when I say that we are all cheering you on, willing to help in whatever virtual way we can. For now all I can say is
and I will repeat: remember what it's like to breathe?