Kind of a rant.. but what should I do???

Sorry, long post, but please read.

My boyfriend and I moved into a new 3 bedroom house and he let his brother move in because he had nowhere to live. His brother was informed and agreed to $100 a week for rent (We have to pay $1200 a month so $400 a month for him is fair). We also informed him that his girlfriend is not allowed to move in or stay for a long time. His brother does not listen at all. He hasn’t paid a dime in the 2 weeks he’s been living here but has money to go buy things for $350. He leaves food out that my cats have gotten into and has made them sick, which I have asked him several times to take care of his food. He smokes in his bedroom (still our house and I am NOT okay with it). He lets his girlfriend come over with her child and they don’t watch her so I walk in the hallway and see PERMANENT MARKER ALL OVER THE WALLS. Pretty much whenever you try to ask him to not do something, his response is “I don’t care” or “get the f*** over it”. I’ve tried to have my boyfriend talk to his brother but every time I try to talk to my boyfriend about this stuff, he just ignores me. I told him I don’t want his brother here anymore, and I’m about to tell him that I’m moving back in with my mom until he either sets some rules and enforces them for his brother, or the brother needs to move out. I just don’t know what else to do, but it’s stressing me out and I can’t take it anymore. What should I do??