You might have a moral point, @Pompeyssy, but legally, OP is on the hook for the joint mortgage until the property sells. The XP has done nothing that would change that (even if the evidence warranted a restraining order, which it is a long way from doing)
They both made a mistake in buying together before renting together or one moving into the other’s place, especially given there was a child involved.
Yes, he isn’t a good person to live with a child, but he’s trying to do the right thing now.
ETA: and he didn’t fuck up her first time buyer status, OP took an adult decision to buy with him.