Hi Blulady,
Does your husband have any residual eating issues or complete loss of appetite? My recommendation to those trying to put a little weight back on (and few nutritionists would agree) is to eat whatever he desires. Eat a whole pie if that goes down well. After going through the battle it isn't going to make much difference at this point if the correct nutrition balance or whatever is in the food he eats. You can visit that after his pants stop falling off. In the meantime he should be rewarded with whatever trips his fancy.
Most of us have had eating issues after radiation, dry mouth, etc. Some foods no longer work. Bread for example might not be easily swallowed but if you use real butter and lots of it, yummm. Four weeks out for me my wife made me a custard pie which I ate within a day. Of course I won't do that now but back then, why not?
Let me know what his abilities are food wise and we can offer up some ideas can you? Lots of folks on this feed who have some great ideas.