Mitzi has the itches too and I don't like to put all kinds of medication on or into her. But for some reasons it helps her when she wears a soft t-shirt (I make them out of my old white t-shirts.) She scratches much less. As of chewing her paws it helps her washing them with clear water several times a day, especially after she went outside (I'm using
flitered tub water.) Our Vet recommended Physoderm as a shampoo and that keeps the itching down too.
Hopefully your little big boy can get better pretty soon! It is so heartbreaking when we can't help them right away...