Congrats on finally getting thru the rad treatments. Its not easy at all and the road to recovery will be a very long and sometimes frustrating time. The most helpful thing you can do is continue to push the high calories and hydration with attempting to maintain the 2500 calories and 48 oz of water every single day for at least the next year. His body has been thru the war and needs lots of fuel to rebuild itself.
High protein whey powder (unflavored) is an excellent additive to drinks. It dissolves easily and doesnt alter the taste. Add it to a shake or smoothie. Make sure to check with your husbands doc first as from what Paul mentioned a while back his protein can impact the kidney function in some way.
Here is the list of easy to easy foods. Try to make a goal of having your husband try say 2 or 3 new foods a week. Be prepared for the first 3 or 4 weeks for everything to taste like burnt, salty cardboard charcoal. Gradually that will change and one day out of the blue your husband will be able to taste something and that will be his new favorite food.
Hang in there, this horrible ordeal is almost over. You did good!
Easy to Eat Foods List