You're not going to find out much my tracing the IP's especially if he's using Yahoo webmail. Also, it's highly unlikely there's a real Jack Pettins--if so, it's probably a stolen id
Anyway, the best strategy with Amazon is to *call* them and say that your order looks fishy for the following reasons:
1) The seller has only been active two weeks
2) Previous items with positive feedback appeared to be small value items used to build up a rating
3) The item in question was offered at an extremely low price (below typical market value)
4) He was selling a *large* quantity of this item (only Amazon knows how many)
5) He provided *instant* communications just before and after the sale
6) Said the item shipped but did not provide any tracking or delivery confirm #
7) No replies to emails since last Friday

Negative feedback has started to show up on the seller
9) You know of many other buyers with the same concerns
Ask Amazon to begin an investigation on jpettins. If we all do this it will quickly flag his account as a problem that they will check out. Most likely, he and the money are gone.