Driving me CRAZY

Okay so here is a rant that I just need to get out. So I live with my MIL and FIL, don’t worry it won’t be for long because we are looking for a place, they have a cat they have had for 15 years. When I moved in they never gave him attention so I felt bad and couldn’t live in a house with a cat and ignore it. My MIL has declared that he is MY cat without consulting me. She started feeding him wet food in the morning way before I moved in and he meows like crazy to be fed early, early in the morning. I have taken over feeding him because now she says he is mine, because I gave him the attention he was not getting. He always would cry at her door in the morning for food and we dealt with it without fussing. Now that I am feeding him he wines at our door and my MIL goes nuts and throws shoes at him and makes a point to tell me that “your cat woke me up early, again.” Which I am sick of hearing because he is NOT my cat. She has taken over doing the litter box because I am pregnant and all I hear about is how she has to clean it “blah, blah, blah...” Then if he pukes in the hallway, hairballs and such, she will ignore it and wait for me to notice or step in it to clean it up. I am not lazy at all I clean up after myself, my husband, I cook and I help her clean the floors, dust and I clean our room and bathroom, dishes etc... This one thing just pisses me off so bad because I am done hearing about what “my” cat does even though they had this cat for 15! Years. They didn’t want to deal with him anymore so they pawned him off on me.

P.s. they will not let go of their baby boy and want us to live here and whenever I bring up that we are looking they get upset and say we can’t leave.