I'm sorry to hear of your father's plight. I will be praying for you, your father and your family. I don't know how old your father is, but hopefully he lived a long, fulfilling life. I pray that if God's ready to take him, he takes him painlessly.
Pop died at 69 in the early 90's of brain cancer. There was nothing we could do but stand there & watch him die. Just be there for him now. Maybe say the one thing to him you never could before.