So why the carp did your mom choose to live with him in the first place if there are that many things wrong with him?
That being said its safe to assume that when a relationship has collapsed like this it didn't START that way. No one would willingly enter a relationship if they realized it would descend like that.
This is more or less it. He started off pretending to be an incredibly nice guy until he got us to move in with him, then it went south from there.
We wanted to leave shortly after moving in with him, but my mom kept putting it off thinking he would change. Plus when she tried bringing it up with him he would go ballistic and start screaming. Once he even phoned my nan and started screaming at her, blaming her for the fact that my mom wanted to leave and telling her to never come near me or my mom again.
About a year or so later the house we were in had to be sold, since it was the house he and his wife had owned before they had divorced, and a part of finalizing their divorce required it. He assured my mom that things would change once they got a house together, and my mom believed it because she would also own the house, and thought that that would mean she would get a say in things. The only thing that changed is that the amount of debt my mom has went up. It just kept getting harder to leave as time went on. And he kept acting worse as time went on; especially after his own kids left him.
Then he saw the house we are in now, declared that he wanted it, and my mom and him spent a ton of money to have it completely remodeled.