It doesn't sound that bad, but rather good, if he is still drinking 3-4 ensure's, only lost 10lbs, but doctors do get concerned when 5% of your weight is lost unintentionally, so ask about that, and there are ways to increase calories, fat, protein to these drinks, make your own, and everyone's own pain is the worst pain, but it does get better. In another week or two the rope mucus should start subsiding, and he will start to feel better, less nausea, vomiting. After that, I felt best at three months, then 7 months with eating, some taste, with something different improving at each phase, and some may take even longer like dry mouth, which may never fully recover, but may be good enough, and may take some a year or two for some ailments, including energy, blood chemistry, etc to resolve, and other co-factors may be involved, making everyone different. Basically it takes time. It's not a sprint, but rather a marathon, so both pace yourself, and your expectations. Radiation keeps working just as long as your treatment lasted, so keep doing what was done during treatment, and beyond, since it does not end once treatment ended. The main thing is to be cancer free, and most everything will follow. If you have any question in recovery, of course ask your doctor(s) first, but asked here, and you may tell us something new, different.

Good luck.