what should i do with my parents?

they have been arguing for exactly a year from today. i remember 9/21/11 me witnessing my father hit my mom right in front of me, from there on, they'd always fight/argue because my dad thinks my mom cheated on her. everyday, it has affected my 8th grade year. now im currently in 9th and today they still fight. it makes me really sad because they want a divorce, and how they hate each other, and that they want to kill each other. they say this all infront of my bro and i. my dad always calls my mom a slut and what not, and all of that stuff, and my mom fights back, but that cuases more problems. i'm tired of all of this but i don't want them to divorce. if they don't/do divore either ways i'd still be sad because my life wont/isn't the same anymore. i hate the fact that in my culture ( i'm mexican ) it's traditional to have a Quincenera, my family has been talking about this since i was young, they always wanted one for me, but now once i turn 15, i can't have anything because my parents can't even have a normal conversation w.out arguing. on my 14th birthday, i went out to eat only with my dad becuase my mom didn't want to be in the same place with my dad. how does that sound? made me extremly sad not having both parents there for me on my 14th birthday. as a freshman now, i decided to work harder in school because if they do divorce, my mom won't be able to pay for all the tutition for my college, ( i also have a brother that's a junior in high school now, my mom is planning to move out w/ out her and my dad divorcing, but they wont be able to pay all of his college if its expensive, you know? so im trying to do good in all my h.s years, ) but i mean, it's hard for me to concentrate because every morning before i leave for school my parents are arguing and it gets to me, every single f u -- ck -- ing day. :( i miss the old times, what should i do? i tried talkignt o my parents but they want nothing to do with each other whats so ever .. and i don't want them to divorce because if they do i'd have to go with my mom, and she wont want me to be able to see my dad because she thinks he'll hurt me or something ... what should i do?