It's actually a healthy thing that you're feeling these intense emotions and not bottling them up, causing yourself grave mental and physical problems. After all, your rage is justified toward someone who abused you. Too many people today seek to selectively numb an emotion that they find undesirable, such as anger, sadness, and frustration. Because dulling just one emotion is impossible, though, they wind up dulling all of them with anti-depressants, illegal drugs, alcohol, food, sex, gambling, porn, and technology. It seems we want to do anything but feel our feelings and deal with them.
When I was in counseling for depression, my therapist would always say, “Depression is anger turned inward.” My sadness had taken over my life, paralyzing me because I had never dealt with the fury toward my dad. Instead of expressing it, I had turned it against myself with a cruel inner voice that attacked my intelligence, my appearance, and my personality. You're in a much healthier place because you understand the exact source of your anger (your dad and stepmom) and don't blame yourself.
You can use your anger in a constructive way. Instead of being a victim of it, deal with it in positive ways such as exercising, talking to yourself in an encouraging way, writing in a journal, meditating, spending time in nature, talking with a friend, seeing a therapist, practicing gratitude, developing a deep spiritual life, volunteering, and being kind to yourself. When you treat yourself with tenderness, love, and respect, you'll no longer want to be weighed down by your rage. You'll no longer want to give your dad and stepmom power over your life.
You've had a tough time of it, so let yourself grieve the loss of a healthy and loving family. Forgive your dad and stepmom and vow to do better in your own life. The philosopher, Friedrich Nietzsche, said, “To live is to suffer, to survive is to find some meaning in the suffering.” If you can help others by sharing your experiences and showing them compassion, your pain will have a purpose, and your anger will diminish.