What to do next

Ok so a while back, I posted that my parents treated me like a child. Most responses were to get a job and move out. So I got a job. I'm a busses and I know it's not much but it's still a job. Last night, my parents and I got Into a physical fight. I'm 20 years old and I'm forced to live with them. We got arguing about how if I didn't like the rules then I should go. My mom have me the perfect excuse to finally leave after takin enough emotional abuse. So I got packin and when I let them know I was leaving, that's when it got physical. They forced me back into my bedroom, they tossed me around. My parents weight a good 400 combined and I'm only 100 so I'm pretty defenseless. My parents threatened my friend who was coming to pick me up and take me to her place for a day or two. That was the original plan to leave for that long them come back, but if I can't even do that, I have to ask for permission to move out, after I got a job, I go to school, I pay my own tuition my fiancé is financially stable and everything is jut right, then I'm certainly not staying here much longer. But the problem is, I'm not sure what to do. I've got work in two hours and they're not letting me leave. I can't lose this job. I've turned in 200 applications and this one I got offered. I will not stand being treated like this when they were the ones to say "fine. It's your decision. Do what you want". I need o be treated as an adult and I can't be here anymore. So what do I do? I'm being held against my own will in my home and i cannot be here.