I wouldnt worry mate, defo send the email to ebay and get him banned, i would call his bluff personally because if anyone thretened me or my family i would ****ing kill them.
why dont we all club together and email the twat with a warning that we stick together on here and whatever he dishes out he will get back 10fold
but on a calm note, dont worry at all mate, i had one like this and i sent back "what time and where?" and didnt get a reply lol
the sensible thing to do is report it to ebay, and report it to the police, they will then think twice about threatening people like sad cunts.