threatening to Kill /Abuse

Here's a little back story my mom died a year ago and my dad died years before that. Meand my brother live with my aunt and uncle. My uncle got 12 children by 5 women and in the past beat my aunt and now beats his kids when they mess up and now she's trying to move away becuase she tired of him. She said that a year ago but anyway my brother smokes and my uncle is a drug dealer. My brother has bongs and let's our older cousins use them when hes gone. I guess the bong got left out and my uncle broke it and threw it away. I don't really care about that but then hes going to tell my brother when he got back "If he leaves any weed around and my kids get took I'm killing you" saying this over and over. Little did I know he says things like this to my brother all the time. And they also talk about how they should beat my brother but never did it.Even though my brother is 17 and I'm about to be 15 this brought tears to my eyes. Now I know in other states you can move out at 17. My aunt gets social security for me because both my parents are dead. People keep telling me that she shouldn't just be giving me and my brother 200 because we get way more then that. Plus that 200 has to buy us clothes,shoes, and sometimes use it to get food because sometimes there is no food.So I think I should start talking to my brother about me and him moving out. I just need some options on this? What should I do?