pustules indicate bacterial infection, but it could be yeast as well...
I'd also consider Epsom salt soaks, but as mentioned, its pretty key that you keep the feet dry. If its as bad as it sounds, I think an e collar may be in order to let the feet dry out and heal up from the trauma of the chewing and the licking for at least afew days.
The spray mentioned will help, Gentocin and betamethasone, what I know of is Topagen - but betamethasone is a steroid, and I'm not sure what the vet will feel about topical steroids. You could also ask about bathing the feet in antifugal shampoo (but do ask), it should have Ketaconazole in it? I think. The brand I had used with my dog is Nizoral.
I can only please one person per day. Today is not your day, tomorrow doesn't look good either.
"You didn't know of the magical powers of the break stick? It's up there with genies and Harry Potter as far as magic levels go." SisMorphine 01/07/07