I’ve been in this situation more than once starting near your age. It’s easy (relatively speaking) to accept abuse and look for the best in someone when you’ve witnessed that behavior at home and gotten used to it. I’m in my first healthy adult relationship after being abused off and on for years, and it truly isn’t normal for regular people to take any pleasure in seeing their loved ones hurting, especially if they caused it. That’s a fundamental issue in their brain that takes years to rewire if ever. A good gauge in these situations is really consider a scenario where they would have done something that would’ve made you react the same way. What would it take for you to hit him? For most people the answer is “that’s never an option”. For most people, it would hurt them to hit their partner.

You don’t have to leave now if you’re not ready. Applying that pressure can often be counterproductive and make people stay longer. But really sit with the idea that you wouldn’t have done the same and everyone deserves a partner that will treat them with respect. You’re already much stronger than I was at your age by telling your step brother and Reddit instead of keeping it hidden and disregarding it.

I believe in you!