Boyfriends Stepdad Fought My Bf (17)

(I'm sorry if I don't explain this right, I am stressed out, I don't even know what flair to use)

So his mom and stepdad have always been really weird and rude, and this isn't shocking to me at all. I don't know how to summarize this, but about a month ago is when his parents started getting worse. His mom locked him outside in below freezing temperatures with no socks or shoes because she got upset that he was going to the bathroom before doing the dishes. (This is just an example of the many things she has done before) She has repeatedly been taking things away from my bf for no reason (I am not exaggerating, she comes up with dumb reasons out of nowhere)

Ok so she asks him to take the trash out, he says he'll do it and that he didn't realize what day it was (he's usually the only one to do it, so I'm not sure why she got onto him this time when it clearly wasn't intentional) she gets super pissed and goes on about how he never does anything (this is FAR FROM TRUE, as much as my view must seem biased) and goes to take his TV away. He grabs the TV and says she cannot take it away again (this is the 6th time this month)

So picture this, his mom and him are both holding onto the TV with it between them, and his mom pushes him onto the bed, she then starts screaming for her boyfriend, saying he's in top of HER (she does this type of thing very often unfortunately)

He comes in the room and gets into my boyfriends faces and starts talking shit (he does this a lot, I should also mention he drinks and uses drugs, I don't know if he was on anything at this moment)

He threatens my boyfriend and gets in his face, I cannot remember this detail too well, but he was doing something physically that resulted in my boyfriend punching him. This is extremely out of character for my boyfriend, he's had people in the neighborhood threaten to shoot up his house, threaten to beat up him and his family, threatened to run over him, and he hasn't ever done anything to them before. (I'm so sorry there's so much to explain, but the police don't care about what the neighbors are like and I'm not sure why, I wish I could give examples of what I mean but it would be so much more typing)

ANYWAYS... his stepdad punches him 10 times in a row, and eventually calls the police on my bf. They both get arrested, but only his step dad goes to jail. Now his mom is going to less charges on my bf???

I'm SO sorry if this is so confusing, I tried explaining the best I could, but please don't underestimate his mom, she is such a bad parent ???? I have never met anyone like her and she is incredibly manipulative. She is constantly trying to put my bf down and telling him everyone hates him, and also always said a lot of bad things about me behind my back for no reason ???? like when I didn't have a job she would call me a LOT of bad things (mind you, she lives off of her ex husbands child support and has NO job ????) and I didn't even have a car in order to get a job!

I just want to know what he can do, she's actively trying to ruin his life, she even tried lying about what happened! (which she does an awful lot)

I feel really sick, he hasn't even graduated yet and she's trying to ruin his life. There's so much more that she's done but this is already such a long post, which I'm really sorry about.