I Can’t Deal With It Anymore? What Should I Do?

I don’t want to bore anyone with my story, but I’m really conflicted about what I should do. Beforehand, I guess some basic things about me are that I’m 18 years old, male, live with my twin brother, mom, and dad and I’m about to go to college. I don’t have a job, and therefore I have no money of my own to afford psychological help, counselling, etc.
So this was the situation that happened to me tonight. My brother was shouting and swearing (by the way, this isn’t anything new to our family). My father comes into our room and immediately does the same thing by yelling at my brother (again, nothing out of the ordinary really). My brother starts swearing at my father and my father’s screaming his lungs out. Finally, my dad decides to leave the room, but not before slamming the door dramatically and almost knocking the thing off its hinges. I’m assuming that he tells my mom his side of the story, because within the next minute, she opens the door and starts shouting at my brother. My brother (who’s kinda mentally unstable and has a therapist), thinks that he’s tough stuff and decides to start shouting at my mom. Long story short, my brother actually got up and started attacking my mom, prompting our dad to come in and attack him, along with our mom, all of which happened while I was standing there watching the whole thing unfold. Eventually, I can’t take anymore of it and I start screaming at them to stop it. They don’t when I yell, but when my mom screams at them to stop, they listen. Then I try to be the voice of reason, telling them why that’s wrong and dysfunctional, and that fighting like that isn’t something that a family should do. Of course, my voice is disregarded, even when I start crying. It’s like no one is even listening to me anymore.
So now I’ve told them that until they make up with each other, I’m not talking to any of them. I’m tired of crying and I feel really whiny by making this ultimatum, but I’m not sure what else I can do. I was really tempted to call 9-1-1, in fact. Help???