Step kids, leaving a relationship

Today my boyfriend left for work. I was home alone with my son when his kids got off the bus. This is like everyday it’s fine. Iv lived with them for over a year. I heard the kids fighting in the room and like it’s what ever kids fight. It’s an 11 year old boy and a 9 year old girl. But then I hear the girl crying so I go in the room and she’s on the phone with her dad and she’s crying and she’s saying the boy hit her in the face. I’m telling the boy he needs to leave his sister alone, it’s not just his room, she can be in it if she wants. And he tells me shut up that I don’t pay rent. So I walked over and unplugged his PS4 and went and locked in my car. My boyfriend is furious with me for bothering him at work, which first off I didn’t call him his own kids did, I just called him back to let him know that I was issuing the punishment of taking the ps4 and that it would be in my car so to pick it up after work since he gets out sooner than me. And I’m not trying to punish the kid for ever but seriously your a kid I’m an adult you are not going to speak to me like that. Nor are you going to hit your sister. I did end up calling the kids mom to pick them up, which she is suppose to pick them up but the boy refuses to go with her. So he lives with us full time now. My boyfriend is saying it’s my fault for escalating the situation I shoulda just left the boy alone. This kid has anger problems stemming from something before I came into the picture, and his dads solution is just to give him what ever he wants so he’s not yelling and hitting ppl. And I hate that kinda parenting. Which they are not my kids I’m not going to tell my boyfriend how to parent his kids but if you leave me home alone with them what am I do ? Just lock my door and be like oh well they aren’t mine and let me hit each other. Oh I’m expected to drive them to grandmas when I leave for work, and feed them and help with homework. Just not discipline them.

I’m honestly so fed up with living like this, I love my boyfriend and I don’t want to take his son away from him. But what else is there to do. Idk If I’m ranting or looking for advice. Just really sad right now.