Valid case for divorce

Hi, I am a north indian, married to a maharashtrian. Suddenly after marriage, my husband has become overly protective of his family and has physically abused me , if we have a fight over them. He secretly talks to his married sister for long time almost every day, to such an extend that the sister also leaves home to be away from her husband and talk to my husband. So much has the affection grown that if on some weekend am not home, he rushes over to his sisters place. On our honeymoon or any trips that we underwent, the first thing he does is start buying gifts for her. We came to US recently, and had a quarrel early morning, and the next thing i know, is he's on call with his sister. How can a husband be fighting with his wife and then talking very calmly with his family/sister? He has literally spent a lot of his income over her needs, be it her bills, grocery, electronics for home etc. In response, this female rarely calls my husband or shows care. When my husband was hospitalized for a minor operation, his sister didnt even bother checking on him once, and the first thing my husband does is call her up after he's recovered consciousness. I am fed up of this presence of the other woman in my life. Please guide me, I wish to leave my husband and his family alone.