My dad died 30 years ago after it spread to his liver. He was in the study at duke for what is today the standard treatment line for immunotherapy. I hope he was able to help. He died 9 months after his diagnosis.
Enjoy the time you have with him now and be grateful for all the years you've had. Nothing is going to make the loss of a parent "OK" and it will hurt no matter if you see it coming like you are or it's a surprise.
Remember to breathe.