They never asked why he wore an eyepatch; they just assumed it was part of his style. Considering he has a prosthetic arm, they should have known better.
I don't think the village is in a different dimensional plane since Hildigard and her father visited to buy things to sell. I think either Karuto's village has a medicine or food that slows down the aging process, or they did what the grandma did in the flashback and made a medicine that...