Help an 18 year old get into a better situation

Hey guys, so I'm in a bit of a texas pickle. I'm 18 years old, i live with my parents and younger siblings, and if shit goes any further south in this house we're going to hit mexico. My stepfather is controlling and emotionally abusive, my mother enables him, and they are having yet another kid that i am most likely going to have to raise as i did with my 5 year old little brother. I need help to get a car, which is where around 75% of the money is gonna go, the rest towards insurance and gas and maintenance.