I am zero help with the ears.
However, with the food. Many times when switching ANY dog to a rare protein source- they don't eat it because well.. it isn't very flavourful.
If it were ME (keep in mind, i tend to do the opposite of what my vet says as she doens't know a whole lot on dog nutrition- i'm teaching her a bit
). I would be putting her on something like:
Dick Van Patten's Natural Balance® Allergy Formulas for Dogs
either the venison or fish formula. The carb is not a grain (sweet potato) so you can ensure it isn't a grain thing and the protein is a rare source- usually can't go wrong with a fish.
I would be telling my vet that a) IAMS is not a great food at all- you want her on a higher quality food. b) she is not eating the IAMS- she is too tiny to be not eating and not liking her food. You have found a rare protein and a grain free food. You have to give it at least a month to see a difference- so hang in there. If you are going to give her treats- stick with fruits and veggies.