[link] <--- a list of hotlines Please, please report him. To the police. To CPS. Keep calling, keep trying. You're not only in danger, your sibling is. He is being incredibly abusive and needs mental help. I'm so sorry this happened to you and I hope your situation gets better. ):
It's incredible how hard it can be to get help in such a situation. Be it from school or the police etc.
For example a friend of mine had a similar situation where her dad "got smart" after almost getting caught and started to make sure there are no mark left after a beating. It got really bad one time when he took her to nearby woods for a beating - scared the hell out of her. There were no marks on her though so she made the bruises on her own and went to the police with a recording she made earlier. She tried to get help for months before that incident but people got really interested only after she got the "proper evidence" -_- At least she FINALLY got some help and a restraining order.