Didier,
It sounds like you have finally been able to pinpoint why this is bothering you so much, which is good. You did the best you could as a caregiver for your father. The fact he did not appreciate it, is neither here or there. It is unfortunate that he left you with such hateful words, but he probably didn't mean it.

The last 11 months of my fathers life were hell. He was home with my mother and nursing care. This man, who was in this condition because he took off on his walker in them middle of the night to reach his beloved wife who was in the hospital, said some of the most awful things to my mother during those 11 months. I know she knows he didn't mean any of them, but it hurt her. She wanted him at hospice in the end. I think this was the reason. Think about getting some therapy to discuss this. I think you will find that you are not alone. You did the best you could.

Take care,
Eileen