Did you ask the doctor what was the basis for his concern? My guess is that like most doctors, he drinks the DEA Kool Aide so he is basically clueless about the differences between hulled hemp seeds (the technical name for hemp seed hearts which sounds better for sales)and marijuana. There is no -- or barely measurable levels of -- THC in hemp seed hearts.
Even sites for pregnant vegetarians promote hemp seed hearts.
Even main stream media sites like CNN promote hemp seeds
CNN: eat hemp seeds
As far as nutrional info goes, lots of web sites tout them but Wikipedia has the best nutrition chart.

All that said, if your husband's chemo doctor has a different reason than mistaking hemp seeds as some kind of pot, I would probably not use them since there are interactions with some nutrients that reduce the efficacy of the chemotherapy. I have not seen any medical studies nor any scientific evidence for hemps seeds doing this or even any blogs or posts. In fact, the Internet is full of the opposite: crazy claims that they will cure cancer (they will NOT). It is reasonable to ask the doctor for his reason. If he cannot articulate one or worse, gives the goofy DEA versions, that's different.

Also, unless your husband is highly motivated to avoid a PEG, he is going to have a tough time without a feeding tube. Even though I have been the major warrior in the old PEG wars advocating the benefits of total oral nutrition during TX like I did, I acknowledge that it is not the best way for many patients for many reasons. Yet for me it was the best way for psychological reasons and being able to say NO to the PEG and feel like there was at least one thing the cancer was not stealing from me kept my spirits high during TX and my attitude extremely positive.
Charm