Advice for semi-adult out of control brother?

My brother is 20, but since he graduated high school, he has been completely and totally disrespectful towards my parents, especially my mom. He's gone from job to job, keeping them for no more than 3 months, deciding he hates it there or just doesn't feel like going to work. He attempted school at the local community college, but either failed out or skipped class altogether. My mom supplies him with spending money, gas money, and a car whenever he wants to go out. His life is in shambles and he doesn't realize it, or doesn't care. He OD'ed two years ago on vicodin and energy drinks, but got his stomach pumped at the hospital. He smokes, dabbles in drugs, and drinks. He has been dealing with the fact that he's gay for over two years now. He sleeps all day, then wakes up, asks for money or cries and throws fits until he gets it, stays out all night, drains the car of any and all gas my mom put in the day before, and returns anywhere from 5 am-10 am and does it all over again. He's currently being sued from an ex friend of his for a minor accident they were in a few years back for pain and suffering, and he's refusing to take care of it, placing the burden on my parents. He's constantly in a bad mood, swears at my mom when she simply wants to talk to him. He's supposed to be in therapy, but his therapist knows he lies about how he really is, and he refuses to take his medicine. Whenever my sister or I try to talk to him, he lashes out. He got so angry at me once, he kicked me in the stomach. When I try to talk to my dad about it, he says he'll talk to my mom about it, but she yells and screams at him, then comes to find me and tells me to keep my nose in my own business. My thoughts are that she takes this abuse because he's a) the youngest and therefore "the baby", and b) she's scared she'll lose him for good. I know he has anger issues, and he has been diagnosed as bi-polar. He really needs a wake up call. What do we do?