My sister's brother choked me, but she's still with him, what do I do?

My sis had been staying with me for a year because my dad died, but she was living on the road with her boyfriend. And for a while, it was ok, but, they insisted on cleaning. Now I know that's not bad, but the problem wasn't that they were cleaning the problem was, they got on my case about it. I had never told them to clean, nor did I question it. But, they didn't seem to realize it. so, I decided to ignore them and just not clash. btw, I should point this out early on...I'm an 18 year old fat kid, my sis's boyfriend is a 27 year old buff guy, so...kindof intimidating lol. I didn't deal with it til he got angry with me and stole something from me, the house we live in is mine, my father passed it on to me, and my father left me the computer...he made me promise never to tell anyone the password, my mother was living with us while I finished school, so she asked how to log in, I wasn't there, so I told her to wait, and idk how, but my sister's bf changed the password. I lost it, and yelled at him, but eventually decided avoiding him instead, until he kicked my door in. I ran to a friends cuz that's terrifying. but the next morning I came back to him hanging out in my living room as if nothing was wrong...I lost it again, but ran outside and proceeded to punch my fence, I decided to forgive him just to get rid of the conflict faster, but, over time, he got angrier and angrier (still about me not cleaning despite me never telling him to do so) throwing little tantrums and breaking things, stomping on groceries, until one day I was pushed to the edge, and left before I did something I'd regret, I came home later that evening to see a turkey dinner, I refused to eat it, my sis and her boyfriend made it, I called them scum and went to my room, my sis stacked the dirty dishes of everyone who ate the dinner (my whole family) outside my room and told my mother I did it, making her clean it up. I snapped, and ran out and scolded my sis for her foulness, at which her boyfriend came out and glared at me flexing so he could intimidate me, but I was done with that, I got in his face, he yelled at me for calling them scum, and I yelled as loud as I could at him, "You are scum!" he grabbed me by the throat and when told he would go to jail, he said, still glaring at me "He's 18" I went to a cop 2 days later at my highschool...I didn't wanna press charges...I just wanted them to leave, So I filled out a police report just as a precaution to what he may do in the future...it's been about half a year...and my sis is still with them...and we haven't spoken at all...my mother wants me to forgive her immediately because she wants her daughter back...but...she doesn't see what it's done to me psychologically...what do I do...and how do I do it...thanks for all of your help.