If I can jump in here, I too tried five different nausea meds until out of frustration my oncologist put me on Larazepam, which basically fogged me at night so I could rest. Mind you this was for the radiation sickness only as I did not have Chemo at that time. Everyone reacts to radiation differently. Radiation to the head and neck seems far worse than most.
There just isn't a lot to comfort your husband. But remember, this sickness isn't forever, just for a while. By spring things will look better and that's not far away. It isn't a pleasant fight by any means but it does take courage.

@cris2 I did only had nausea a few times, and in every case, I was reminded to take them at the very first sign of an issue, as it is easier to go keep it away then to get rid of it. A few times, I just decided to take it as a precaution.

Please just remember, the treatments will end and things will return to normal, albeit what could be a new normal. So just grind, grind away and stay focused on the prize - being cancer-free.