My advice is to limit your interactions with him as much as possible. If your mom or step-dad notices and asks why, I’d just be honest and say that he scares you. Eventually he might realize that he doesn’t have a good rapport with you and will work to repair it. This may or may not be worse than what he was doing before.
If he tries to tell you how to feel, say, “don’t be scared of me,” just agree with him and don’t actually change anything. If you’re feeling froggy ask him to not throw anything please.