Also, as a human with food allergies, I know there is no such thing as generically "hypoallergenic" food. She should probably start him on an "elimination" diet - feed him simple things, like plain boiled chicken, and see how he reacts to that. All the issues could be related to the food allergies - as sometimes it makes the mouth feel itchy, and chewing on something relieves that.

It may take some time to figure out what is safe for him to eat, but starting with just chicken, and then adding some rice, and seeing if things calm down, will then enable her to slowly add other things, cautiously, one ingredient at a time, until she knows what is causing his issues. Has a vet checked those poor paws? Is it possible he has nerve damage that is causing the poor thing constant discomfort that could maybe be remedied?