Death threats and verbal and physical abuse from my father

I'm 17 years old teenager my father do domestic violence he gives death threats my mother my brother and I, about several years he tried to kill my mother he beats our mother and trys to kick her out my mother's parents died years ago he doesn't let my mother to meet her siblings my Father is not in good terms with his family members and others relatives he wants everyone to obey him he also beats us(me and my brother) my mother doesn't file a case cause we are broke without him that's always makes him stronger we dont have anything me and my brother are underage our mother isn't not much educated he sometimes calls my mother prostitute he often tries finds excuses to argue and tells that we are the one who were wrong he always tells us dont cross your boundries or you will be food for Street dogs it so depressing i often gets nightmares related to this, teachers judges me in school and make fun of me nobody asks what's wrong with me i dont know how my mothers feels about this she is over here just for us we dont have anyone except him i often saw her crying just give me some advice how can i help her