I had the surgery in September of 06. Following the surgery, I had additional chemo until January 07. I gradually had my sense of taste change such that there were very few things that I could eat. I couldn't stand beef, coffee, even water. I forced myself to drink Ensure and filled up on snacks and candy that I could stand. The sweeter the better and in some cases, the tarter the better. About 6 months ago, my taste started to come back to normal. Now I enjoy a good steak and just about any of my favorite foods. The only problem I have now is that I cannot eat more than a 1/2 portion of anything. This means that I am always bringing a doggy bag home from the restaurant.
Tell you Dad to hand in there and stick it out. It will get better and in the meantime, eat whatever he can get down, even if it is only snacks and candy.