As said, each patient reacts differently, and in fact, each treatment is different. I had 33 doses of radiation to my throat/neck, and three doses of Cisplatin, and only 6 months later, a limited neck dissection just to make sure (nothing there, phew!).
In my case the steroids and/or the Fentanyl and/or the whole physical slam did a number on my head for a time. I then suffered low energy and insomnia for months. By the way, just coming off the Fentanyl patch can, for some, be a huge and extended challenge! It was for me.
I also suffered degraded short-term memory, and was very easily overwhelmed by the slightest uncertainty.
What I can say is now, just about ten months from the end of my primary treatment, I think I am starting to see the light at the end of the tunnel. All of my various complaints have very very gradually improved. Oh how I longed for a "sudden" return to "normal" sleep, but this never came. However, I am sleeping better. My energy is pretty good. I'm getting out to jog, and I'm just about to start working again. My memory is returning, and my optimism to face uncertainty is returning. I hope to improve lots more, but it's coming.
I can relate to your husband's concerns about returning to work. I couldn't have done it a few months ago (or it would have been very very challenging, at least). But now, I'm feeling ready.
Time, patience, nutrition, exercise (when you're ready). It really is true, it gets better. At times it really didn't seem possible, but it has.
Good luck!
-Seth