So you're saying that spot now looks completely normal, except for the fact that the shed always gets stuck there? That's odd- it's as if it's not really healed all the way. Maybe a vet could see something (under magnification) that you can't? And have another suggestion for topical treatment? I've never heard of water soluble Betadine causing such an issue- only ointments (& only the ones that are petroleum jelly based). And a year is an awful long time for that skin to heal completely.Who knows, maybe in another year...
You could also just wait & see?