Sounds like he might be a narcissist. If so, you might have wounded his fragile pride and now he's hell bent on correcting it so he can maintain his inflated view of himself. This happens in guys who aren't narcissists too, who just fixate on things. Could be a little OCD too, which would explain his obsessive behavior.

Call-block's a great idea. You might also be able to *69 his number (after waiting a little while) to make sure it's him and ask him to knock it the eff off. You did do a nice job letting him down though, in my opinion. Kudos!