I agree that another vet visit is in order, but I also remember reading somewhere about yeast infections in dogs paws. This along with the fact that he was on antibiotics twice may well have led to yeast overgrowth/infection in his ears and paws. A friend of mine used to use this powder and couldn't say enough good things about it for keeping her beagle-mix dog's ears infection free:
Thornit Ear Powder - original 1907 formula from K9 Centre
Might be worth a try while you're waiting for the vet visit.