Sorry, for the loss of your father. I lost mine two years ago, he died in the hospital . Lung cancer, I tried to talk him out of the operation. No luck. Had same thoughts as u thought I should have tried harder. In the end we are responsible for our own lives . Our dads made their own choices and suffered because of them. Nothing we could do. I remember my dad every day. Wonder what he would have said or thought about this and that. Sometimes it makes me laugh sometimes I cry.
How is your mother, has she been check for AIDS? Focus your attention on what you can do for the living, yourself included. Your dad is in a better place than he was. There is bad stuff in the world, but there is also good. Enjoy the good , reject the bad. Find the joy in each day, I bet that is what your dad would want.