The "private email" is allowed, sort of, but frankly it is sketchy. Either he will try to move you to an "off-eBay " transaction (which is safer than sketchey sellers think if you pay with Paypal backed by a credit card) or he is a paranoid and hysterical seller who will be a pain to deal with.
I'd move on.
Actually, I would hit the Report button, tell eBay I suspect that the seller is trying for off eBay transactions and then move on.