Was that wear pattern caused by the incorrect starter motor. I would have to assume so since none of the flywheels I've looked at lately look like that. Makes me wonder if the starter motor gear hangs up on those v-shaped notches instead of engaging the ring gear teeth.
Maybe you can have the ring gear turned/machined to eliminate the notches and restore normal function.
If you can find somebody that can remove the ring gear, just take this one off and flip it over so the good side faces the starter.