Facing serious relationship issues by my dad's blackmail

I am 23 now born in an orthodox family where my dad is a person who believes that if women goes out of home, it is meant for a wrong reason. Being a girl here I faced all stupid issues to complete my studies. He blackmailed me for everything since my 10th forcing me for marriage. I somehow managed. And now I am in love. He is working in a private concern. Knowing that he has arranged me marriage. I fought to all extent. He is not at all listening to my tears. He wants me to get married, give birth to child. That's it. I cant accept. He is blackmailing me that he will kill my mom relations and stop my sister studies. He is again planning to arrange marriage even for my sister. He is torturing me mentally. I have decided to elope with a register marriage. He is wealthy enough to play with money. I just want to know whether anything might turn against us by him though we marry legally. I am also ready to give up him being my father. I don't want anything from him. And also if at all I get caught before registering, can i seek police help. I want to know what all can be done to stop him legally.