Cori, I grew up in a home similar to yours. Less severe from the sounds of it, but certainly very similar. When you expect the pain, it not being there only confuses you. With some of the abuse heaped on me from both of them, it took a long time for me to believe I was worthy of emotion and love. I couldn't be perfect enough to avoid the "disicipline," I couldn't be invisible enough to avoid being my mother's emotional waves.
The last time my father actually struck me, I was 15. We hadn't cleaned the bedroom right, I think. He vanished, and I knew he was coming back with the whipping belt (a shortened one with the tip of the buckle removed.) In our bedroom, the area between Cassie's bed and the closet was very tight spacing. You could only access that area by walking between the bunkbed and her dresser, which required a relatively thin person. My father was not thin by any stretch of the imagination. I grabbed both of my sisters, shoved them into the least accessible corner of that area, stood in front of them and said "don't say or do anything, you'll just piss him off more." To my knowledge, not a blow landed on them that day. I think that actually earned me some respect from him, in some twisted way.
I never made the S&M leap. Sex was never intertwined with anything, except comfort and love (you only want what you can't have.) I had an ex withhold sex as a punishment (he never even French kissed me,) but that's a different animal. I knew from a young age that sex and love were intertwined, and after knowing there was no love in his beatings, I can only associate pain with pain and sex with love and sex.