Thanks very much for sharing your story.
My father was not a very good man, I can't say he was as brutal and vicious as your Dad, but he was obsessed with his own pleasure in happy and sad times at our expense and there was little loyalty in him toward his family. He partied merry during the toughest times of his closest family and friends cutting them out as if they didn't exist, when he was perfectly capable to help in various ways. He liked himself too much to allow any kind of sadness of his closest family members touch him.
He spent the last two years of his life in absolute loneliness while struggling with cancer, and his much younger 3rd wife to whom all his multimillion wealth went didn't bother to stay by his side.
We were living in different countries, and were not in talking terms. We don't have a very cohesive family and I heard most these stories after his death.
Looking back, I wish I knew about his situation and that I could have helped him during his toughest times by giving him some company, solace, and peace.
I don't think I see myself ever going as far as you have gone with your Dad and congratulate you on the hard to achieve peace you have found, and the peace you granted him before his death.
Deserved or undeserved, the world is going to be a better place with two more peaceful hearts.