I dreamed about my long-gone abusive father...?

The driver definitely represents some kind of savior. Your mind wishes that there was someone like that there to protect you at that time and someone to be on your side. The driver represents something stronger in your life (maybe like your adult self). It doesnt necessrily have to be a person, but it was in the dream. Basically your mind is achieving in the dream, what it hasnt been able to achieve back when you were 15, standing up for yourself without fear. Sorry to hear about your situation, try dealing with the past to stop the dreams.