Dianne, I share a variation of your experience. My mother was abusive throughout my life. When she was diagnosed with Alzheimer's Disease a couple of years ago, the first sign of her illness was that she became sweet-tempered and docile. She's decompensated quickly within the last couple of months. The first "wave" of my own grief came with the terror of watching this woman, with whom I had had a deadly battle for survival all my life, basically vacate her body.
I was always terrified of being like her--and now I was terrified of losing my mind like her. (It didn't help that I was being plagued with menopausal memory lapses, or that the stress of taking care of her was draining what little mental faculties I felt I had available). I wanted to get past my own fears and grief so that I could do the decent thing, providing what care I could and supporting my brothers and my father as they have stepped up to the plate. I voiced my fear of being like her to a very wise friend. She said, "Daphne. Your mother has never been present. You, however, have never been absent." Those words gave great comfort as I set about the business of pitching in where I could and also continuing to take good care of myself.
Blessings to you as you deal with this grief--not only your father's illness, but a lifetime of hurt. Daphne