He won't. Depending on the state, he may tell you that these types of restrictions are unenforceable altogether, that they may be challenged as unnecessarily restrictive because of the size of the area or time time involved or for other reasons that are specific to that state's law.

But employment restrictions of this type are common enough that "duress" would be the weakest position to take. No one's forcing you to take the job. Might as well sue for more pay since, after all, wasn't it the same "duress" that led you to take the pay you are receiving rather than the higher pay you really wanted?

Personally, I think this particular restriction is a bit over-broad (for example, if there's no business because they don't market and they lay you off, you can't go to the successful school 10 miles away and get a job) . But that's just me and I know nothing about employment law in Ohio.

If you're really concerned about it, speak to a lawyer. It's usually a lot cheaper to get advice ahead of time than have to deal with consequences after the fact.