I don't think you get it, spreading dirt over the internet wont stop fake transactions where it looks like your business did them. I assume you mean your business tax ID number. Reason I assume he will use it like an identity thief is because you don't need that number for tax claims.

You have already placed your identity on the line, I would highly advise staying away from them completely and totally. You've already made a mess of this, don't fool yourself into thinking you have any power online; you don't even know who this guy is.