From your description, it's possible that your cat has an oral infection, either an abscessed tooth, infected gums or sores in his mouth (stomatitis). Because he's pawing at his face, this indicates that it's bothering him in that area. A sinus problem is also possible, as everything is 'connected' internally, and an infection in a tooth or gum may move up into the sinus cavity or vice versa.
The elevated WBC indicates infection of some kind, in his body, so all the treatments he's been given so far, are appropriate, but the fact that he won't eat may be due to discomfort in his mouth, or his generally not feeling well. A hiding cat is a cat in pain and/or feeling poorly.
Put a call in to your vet to report your cat's most recent symptoms, since he was seen, and he might have to be seen again. For the moment, it's important that he eats and drinks, of course, so if you are able, dropper feed him on the opposite side of his mouth from where he's pawing (if he's only pawing at one side); use a 1 cc sized dropper and go slowly. Water down canned cat food and/or plain jarred baby food chicken (no seasonings, onion or garlic) and give him 1 dropperful every 20 minutes for an hour, then repeat in 2-3 hours, if he's still not eating on his own. Also, if he's not drinking on his own, dropper feed him water in the same way; alternate with the food. If you're sure he's not diabetic, give him children's clear pedialyte, as he's most likely dehydrated again. You can also rub a drop of Karo syrup, maple syrup or honey on his gums, as he's hypoglycemic if he's not eating.
I hope this problem is resolved for your furry boy, very soon, and he's feeling back to himself!