Bunnies can still be territorial even when neutered, and one of mine is food aggressive though he has been neutered. We just have to be careful about not dragging out the time between when he realises it is pellet time and when he gets the pellets, he gets wound up and over excited too much. It’s exactly the same as one of my cats and my horse, they dont mean to bite, but they want the food NOW and sometimes fingers get in the way.
What kind of cage is he in? Does your husband have to lean in through the top of the cage or can he walk into it? Smaller cages, especially the pet store ones that open from the top as well as the front can, can cause aggression because they are small so the rabbit is more defensive over the space. They also have a blind spot which makes hands appearing from above quite scary and therefore he may bite in fear.
I know from experience that when one of mine had to stay in his NIC condo for most of the day rather than the 12hours of free time he was used to he got quite aggressive when I went in there. That reverted as soon as he was back to his normal routine.
How do you pet him? Do you get down on the floor somewhere not in his cage and pet him on his level and he still bites?