If it continues: Get help.
If he so much as touches you in a harmful way, you get help. Call your bestfriend, go to a teacher at school the next day, call your local non-emergency number, anything. And if he ever actually beats you, you wait until he is asleep, grab your siblings and go to a neighbor (who you trust) and whether it's 6 in the afternoon or 3 in the morning, you keep knocking until they answer the door.
Most kids and teens refuse to get help because they are afraid of their family falling apart and are afraid of the change that comes with it. I know, because I was there alongside you.
My step dad used to hit me and beat me simply for leaving a spoon and bowl in the living room. I never got help though, because I had a little sister and I didn't want her to go to foster care. Thankfully, I got it to stop by taking the more dangerous route and holding a knife to him. And he eventually moved out because my mom was fed up with his crap as well. But now that I think about it, after taking about 6 years of abuse, I should have gone for help earlier. I would rather have my sister and I go into foster care than have my future potentially be damaged from the trauma than can come with abuse.
But like I said, if he ever hurts you or one of your siblings, you leave and get help. If you're as scared as I was of the family falling apart (which isn't always the case), start of by going to a councilor (school or any at all) and talk to him or her. If you must, simply hint at it at first and ease your way into explaining everything in detail.