Abusive/strict dad

This is the weirdest thing I have ever done. I have never told anyone about my family not even my friends know. I'm 14 by the way.

I wanted to go to my friends house to watch movies and go swimming. I asked my mom and she said yes and that I would have to walk there and back cause she had work. The next day when I was about to leave my dad said I couldn't go and had to stay home. My dad never lets me do anything I'm just stuck in the house the whole day. The only places a can go is school, church and the supermarket. My dad is so abusive I don't think a can handle it. One time he accused he of stealing his $20 when he was drunk and choked me. I told my mom and she told me not to tell anyone or the police will take me. He also hit my sister so hard that she ran away for about 2 hours and it was midnight. I love my mom so much but I don't know why she is still with him. He has cheated lost of times, doesn't even have a job and uses all the money he has on alcohol. My dad has 10 kids, I have a brother and sister and the rest are my half siblings. I just want my mom to leave this man. Every time he does something wrong my mom gets blamed for it. She works every single day from 7:00am until 5:00pm , she even worked 4 hours on Christmas. I really want to talk to someone about this but I'm scared for some reason, what should I do.