Your post reminds me of my FIL's death last year. For the past 20 years he was on medication to keep bipolar disorder under control. When my DH was a child, he was a violent and controlling bully who made their lives a living hell - think children shaking with fear when he walked into the room.
DH went to see him about a week before he died, and came out saying it was the last time he'd see him (FIL was in hospital after a stroke) but didn't go when he knew his father was dying. When he'd died, DH said he felt a sense of relief of being rid of the man, which is so sad (in terms of his father not making more bloody effort and tackling the issues he had). No child, however old, should think that of a parent.
FIL's funeral was all jolly hymns and here is my lovely family and what I've achieved (he planned it himself) and DH was in shreds after it, how wicked he had been to his family and then to play all sweetness and light with his 2nd wife and to show that off at the funeral. Be strong for the funeral if you chose to go, you may find that the version of your father which is presented has little in common with the man you knew.
DH is so much better as a person and a parent than his dad was, and I think he clings to that. What you are seeing is your father's failings, and it's his loss not your's. He's lost a DD, a GD and an extended family.