Open Question: I have all of our in-laws living with us, and I feel they are much too comfortable, what can I do?

Ok, Now with the tricky stuff. I have my husbands entire family living with us. (mom, dad, brother, and brothers kid) They are ruining our marriage, we have been married for 3 years now (together and we have never lived on our own. I know we first started off living with his family, but when I got pregnant we got our own place, which only lasted a few days before his brother moved in. his brother is not much of a problem. To fast forward a bit, his family went through some pretty hard times when the economy fell. Before i knew it they were living with us. My husbands father has a job but for some reason he never has money. They never pay any rent, the are using our luxury car (infiniti) when ever they want, We recently purchased another car because i now am expecting my third child and I need to get around while my husband works, (we have our own company and my husband needs a car available 24/7) anyway, point is i am stuck at home, i am missing appointments, and i have to ask to borrow my own car. My husband feels bad telling them NO! because they give him guilt trips and he tell me to stay out of it and not get involved. My mother in law is always telling me how to raise my kids, always giving my 2 year old a bottle after doctor told me to stop, and is always getting into our personal business. Now as for the my brother in laws kid, he is a horrible child. he is teaching my 3 year old daughter to question my authority, he is always breaking her toys, he hits her, and calls her names that make her cry, we also have to small puppies we got my daughter for her birthday, and he has tried to kill them. he throws them in the air, against the walls, and pulls there legs and tail. he is only 4 1/2 and his mom dumped him off when he was 1. my brother in law does not take responsibility for him, so my mother and father in law have been raising him. He once locked himself inside of the room with my daughter and ook off his clothes, now i was furious when this happened, but they told me i was being dramatic and told me it was my pregnancy hormones talking. I feel that if action is not taken I will have to leave with my parents to teach my husband whos more important, but Im scared they have so much control of our relationship they might start to fill his head about why hes better off without me…
Im very confused they have been living with us about 8 months now!