This is a heartbreaking story and I know how you feel, I had a similar experience with my grandpa, I did not visit him for the last couple of years before he died even though he was like a father to me when I was little.
I am sorry to hear that your last week together was not the best. I know it is easy to feel guilty but your father sounds like a person who would want you to be happy. You can do it. And I hope you have forgiven yourself as it is a horrible burden to carry!
I'm sorry for the loss also. Yes, it was really heartbreaking, thinking that your last weeks or days with someone you love isn't amazing as it suppose to be.
Thank you so much. I will just think right now and put it in my mind that everything has a reason.