It appears that you are in a very difficult and stressful living situation. The way your brother treats you is not right and it sounds like he has an anger management problem. It’s important to remember that it’s his problem, not yours, in that you do not deserve to be treated with violence and disrespect. However, unfortunately because of the living situation, his behavior affects you. The best approach might be to stay out of his way as much as possible, but not in an obvious way. Just try to plan lots of activities out of the home. For instance, enroll in extracurricular activities through school or church, stay over with friends when you can, and so forth. When you are around him just keep your distance but be polite, staying under his radar.
Cutting yourself and not eating enough are not healthy coping skills so I hope that you will look into other options such as exercise, writing in a journal, talking to friends, and listening to music. You would also benefit from speaking with a counselor. You could start by speaking with your school counselor, but you can also ask your mom to take you to see a therapist. Having a safe person to confide in would be very helpful.
Finally, if you brother hurts you again or you are in fear for your safety, you should call the police. You have a right to feel safe in your own home. And keep in mind that you are only a couple years away from being old enough to leave home and go to college or live in your own place. Once that happens, you will have control of how and when you are around your brother. I know things might seem hopeless now, but it will get better.
All the best,
Dr. Holly Counts