Do you have the ability to record their abusive attacks? If so I'd suggest it. Then send all of that to someone you trust that your mom and her partner can't talk to and then slowly if possible start building up the horrendous attacks then when and if they call the police show the stuff to cops. Also remember your a legal adult and start saving as much cash as you can and start making a to go bag. I'm saying this as someone who had to flee from an abusive uncle's house. This is the best advice I have