<human>: Mom and stepdad have pretty much had a shitty relationship for the past 5 years. They have been sleeping in different bedrooms for 4 years now and my mom kept giving him a chance to "change" his abusive attitude. Everytime he gets mad he will break something in his bedroom, punch the walls or just anything in his way, and it's starting to get out of control. He stopped breaking stuff once I started calling the cops but now he just starts cussing at my mom or me even though her 3 daughters are in the next room listening to everything he says and yells. My sisters are 7, 9, 11 years old. It's just not fair for them to go through that. I also have another sister but we're both a different dad obviously.

Now that my mom said there's no way she's going to keep trying to fix their relationship, he got furious and said that he was going to sell the house and that we need to leave when that happens. A month later (today) he said he had someone that wanted to buy the house, which is probably a lie... but who knows. They're not married but the house was purchased under both their names so my mom knows he can't just sell it without her consent. 
She's asking me for help and asking if I know what she can do. And even if we leave I'm not sure if we can afford to get a place. Sure I could move out but right now I just want to help her out, I have a job and been paying for my stuff ever since but I'm not sure if we could even afford to pay for a new house. He's also saying there's no way he's paying child support and that he'll make my mom's life a living hell.

Any thoughts?

Can you condense the text into a few key points?
<bot>: Abusive stepdad threatening my mom, says he will sell house and make her life a living hell for ending their relationship eventhough it has been over for over 4 years. need advice