I always stress how important intake is to everyone. Every single day Chris should be taking in a minimum of 2500 calories and 48-64 oz of water. If he has lost 15% of his body weight, thats alot is a short amount of time. I suggest upping his minimum calories to 3500 daily. His body has been thru so much and it takes tons of energy to rebuild itself. He is only 2 weeks post rads so the radiation is still working and burning up every calories (plus more) that he takes in. Intake must be the number 1 focus starting right now until at the very least he hits the one years post rads mark.
Check with the doc about adding some high protein whey powder to his diet. It will help him rebuild himself. Dont expect to see any weight gain for a long time, maybe not for another 2 years.
Here is a recipe for something I used to make and drink when I went thru treatments. The list of foods might help you also, they mostly have a smoother texture and arent spicy which should be easier to tolerate.
Easy to Eat Food List (All measurements are estimates)
Giant High Calorie Choc-Peanut Butter Milkshake3 or 4 cups chocolate ice cream (regular/full fat type)
2 tablespoons peanut butter (smooth type)
2 tablespoons chocolate syrup
1 or 2 cups whole milk (can substitute half and half to add even more calories)
1 scoop carnation instant breakfast
1 scoop high protein whey powder (check with doc if this is ok)
Blend this extra long to make it very smooth and creamy so it goes down easier. If the shake is too thick, add more milk to thin it down to what works best for you.
Best wishes!!!