I’m so, so sorry for all the terrible things that have happened in your life. Sadly, it’s not going to change until you make some changes. You are living in a constant toxic situation. Although your loyalty to your dad may be seen by some as admirable, it really is killing you. All the drugs in the world aren’t going to help if you use them to help you tolerate an intolerable situation. If you can’t stop letting his treatment bother you, then you need to get out. If you have the desire to leave but not the strength, please consider seeing a therapist to help you. If you can’t afford a therapist, locate the domestic violence program in your area. They can probably offer you some assistance.
It certainly isn’t worth $10 an hour to stay in your father’s employ, especially when it comes with cuss words and nastiness. I don’t see why the idea that he won’t speak to you if you go is a threat. It seems to me it would be a relief. You can make the same or better money (and without the verbal abuse) doing almost anything. Almost anything will have better hours.
I worry that your self-esteem has taken such a beating that you don’t think you can do anything else. You can. Remind yourself of the dreams you had as a young person. Start looking for other work — any other work — just to get free. Then look for classes to develop some new skills. Once you are on your feet, you can start looking for work that more closely matches your interests and talents.
At 40, you still have a long life ahead. It’s up to you to make the next half of your life different.
I wish you well.