I can't bear my dad anymore? Is there a way I can save up and leave the house?

I'm fifteen years old and I've been living with both my parents all my life. In the last couple of years my dad's behaviour is becoming unbearable. Ten years ago we were I could say sorta poor. I mean we had a house and my dad had a job but we JUST had the money to keep us alive. after sometime me and my family migrated to a different country my dad got a much better job and he was very well paid. His profession is a lawyer by the way and he built his way through it. He started from zero and now we can be considered of the upper-middle class. My mum doesn't work and my siblings are around my age. In the country where we live, we cannot work before 18 years and my mum doesn't have a degree so we are living on my dad basically. It might seem ungreatful but my dad is not making us happy. He is VERY short tempered and got even worse when he gained more money. He treats my mum like his personal maid (no exageration) she cooks his food, puts his socks on for him, does his hair and before we had a maid washed his clothes, took care of four kids and all he did was go to work. He is the type that doesn't even communicate with his family. He never sends us anywhere in vacation except to visit his family who HATE us including my mum. And yes he can afford it, his income is $300,000+ a year and still he says he doesn't have the money for it and whenever he does something useful with the money (other than showing off to his friends with it) like for example he rents us an amazing house, we only stay for like a year and degrade our standard because his brothers tell him what a waste of money it is to make your family happy. Me and my elder sister are highschool freshman which means university in 2 years. He still hasn't saved a penny for our education me and my sister are very hardworking and ambitious we are basically A* students and want to study medicine when we are older but we doubt our dad will bother saving up. By the way my mum keeps fighting with him because he is treating her like a servant rather than a wife and never takes her opinion in anything even though she is extremely faithful to him. She overheard him asking another woman out on a date once on the phone IN THEIR BEDROOM! and swore to leave the house but me and my sister convinced her to stay. If my mum leaves he will probably withdraw us from our good education and send us somwhere worse. My mum is just stay for that reason. Is there a way me and my sister can ensure our education? He gives us an allouance even my mum has an allouance but he doesn't give my mum more than $300 dolars a month which she can never spend on herself because he makes her spend it on groceries etc.. what should we do? :(