If he's a young guy maybe he does have to wait for the check to clear to free up the payment to you.
I wouldn't threaten him, I would keep treating him like a gentleman and take him at his word, but I would file the dispute. Like I said I wouldn't get nasty or do anything to make him get defensive.
I would tell him that you are just following paypals' rules. And when everything is settled no one gets a bad mark, and of course thank him for keeping you informed.
The first step in the dispute is they send it to him and wait for an answer, at least he will know someone is watching, he'll have to pay up or explain why not . He has 7 days to answer, I think.
At least he is still talking to you