WOW you sure have your hands full. I can't help with the ear stuff, but for kitty acne, I used to use Neosporin on Goldie's chin acne; cleared it right up.

As for Magoo's dry skin, it does sound like the change in diet may have caused the skin/fur changes. Is NutriMalt like Petromalt? If so, the oils in it will help with the dry skin/fur and any hairballs.

I recently tried Pro Plan indoor cat formula (mainly because Petco gave me a free 4 lbs.) for Mitzi, however both cats LOVE it. I wonder what's in this stuff as they both scream for it! Mitzi's fur is getting so nice and shiny and even fluffier (if that was possible). Now I'm battling keeping Mishi away from it as he's on the special K/D kidney food.

Perhaps a quick call to the vet just to ask a few questions, without having to actually go in with the fur herd. Would your vet just answer some questions over the phone? I know mine does. Good luck!