Until fairly recently, my family used to be a very good one; an example to society of what a good functioning muslim family looks like. Me and my sister were doing extremely well in school and my father had a good job. However, a couple of years ago my father passed away and since then all hell has broken loose. My sister has become even worse than European women, indulging in every sin and even going as far as hitting (!) my mother regularly. The problem is, when I decide to take action against my sister (in place of my father, since now I am the only man in the family), my mother gets extremely mad and she has even kicked me out of the house because of this. It seems as if my mother, in her disability to cope with the situation, is acting out all of her emotions on me. This is slowly ruining my life; I've lost my sleep, my mother and sister but hate me, I sometimes literally have to sleep outside with nothing but Allah to protect me, and it's gotten to the point that I just see no possible solution in sight. It's also affecting my behaviour; because of the insomnia and depression my grades are going down and I'm becoming very intolerant and antisocial. The only solution I see is just going to a foreign country to go to university there (for physics) and leave everything here behind.
In a fatherless family, what is the role of the (oldest) brother according to Islam (In my case I'm the only brother)? Should I replace my father?
What would your advice be to my situation (in accordance with Islam)? It seems I'm really trapped perpetually.
p.s. - I am Sunni