We went through this last October with my Father in law. He had CJD, which came on very suddenly. He lived for 5 weeks with it. For 4 of those weeks, he got worse and worse - combative, couldn't leave him alone (nurses had to stay in his room 24/7), to finally unresponsive. They put him through test after test. Multiple spinal taps, EEGs, etc. Finally, John Hopkin's was able to diagnose him. CJD is 100% fatal. We knew that he would never get any better than he was at that state (could open his eyes, had body tremors, nothing else). My MIL, DH and DSIL made the decision to move him to hospice without the feeding tube. He was suffering and our family was suffering along with him (including 4 young grandkids). He passed 1 week later.
My FIL was only 66 and fairly healthy before this. He just suddenly became disoriented one day. We thought he had had a stroke. This was such a shock to us. I don't feel any guilt about the decision that was made. It's a little different for me because it was my FIL, not my father, but I still loved the man dearly. I am about 99% sure that my DH doesn't feel any guilt about the decision either. He still stands behind that decision and says that if he were in that position, that is what he would want. Not only did it end his suffering (our main concern) but it allowed our family to move on with the greiving process and try to re-establish some sort of normal life without him. We are still dealing with the loss and the kids are having a very hard time dealing with it, but I'm glad they don't have the lingering memories of watching him suffer and just waiting for him to pass.
I will say that when my Grandmother was suffering from congestive heart failure and many other issues at the end, they did not pull the feeding tube. My Aunt just couldn't do it. My Mom still regrets that decision because she feels like it prolonged her suffering.
I'm so sorry for what you are going through. It was the hardest thing we have been through and definitely the hardest decision we have ever had to make. Only you know what is right and what you can live with. But you have to give yourself a break too. There really is no "right" answer when it comes to decisions like this. You just have to decide what the "best" answer is.
Sending lots of hugs your way during this difficult time. Praying that you and your family can be at peace with whatever your decision may be.