Offer him a way out before things get nasty
"hey... listen... I'd rather deal with this personally rather going to ebay and paypal to speak to a dispute manager. It'll be best for both of us... "
Give him a deadline ... and if he doesn't help... then alert other BF members about who this seller is...
You could always... enlist some help from the forum... I've done this with positive response elsewhere... your mileage may vary...
"hey... since I can't seem to get in touch with you.... I've got a relative/ buddy/ LEO friend of mine living in (insert town). I can have him stop by the address you provided to see if we can work out some kind of deal."
Dead beat sellers have called minutes after receiving the email. It's not a threat... It's more like saying... "I know where you live... now answer your ******* email!"