Here is what you do.
First file your FedEx claim with his emails as "evidence" that he sent it.
Next file a complaint with the Ohio AG and the AG of the state he lives in. Our consumer protection dept at the AG's office is actually really good and will pursue anything over $1. Tell the AG that your only reasonable outcome is for the seller to give you the money back and he can fight with FedEx.
Next file a claim with PayPal
Also call Chase and have them flag the transaction as potential fraud.
When he has 2 state AG offices calling him, FedEx investigating it, PayPal investigating it, he will most likely cave.