Some Help Needed?

You can file a claim 4 days after the auction

As mentioned, you have to give him 4 days to pay. You have apparently already contacted the buyer to you are covered on that part. If you should find that he suddenly is NARU (not a registered user) then go ahead and file a dispute with the resolution center.
A buyer still has four days to make payment after you have filed a dispute with the resolution center.
If the buyer still does not pay you need to manually close the case in the Resolution Center within 36 days after the listing ended. If you do not close the case on the 37th day after the listing ended, ebay automatically closes it and you don't receive a final value fee credit. Also, an unpaid item won't be recorded on the buyer's account.

Hope this helps

You can do a 2d chance, but most underbidders either have moved on, or suspect a 2d is because you shilled them. Also, if hi bid was considerably higher, the 2d will be taken at the old hi, for example:

hi $120, 2d hi $108 (forcing $110), 3d hi $90, 2d offer = $91