Heres your escrow solution:
Find someone EXTREMELY trusted. Escrow receives BTC from the BTC seller and the buyer sends the amazon gift code DIRECTLY to the escrow. The escrow is given the login info for the BTC seller's amazon account where he wants the gift card(s) applied. The escrow then adds the gift card code(s) himself manually and if codes are good he releases the BTC to the buyer. Otherwise, if codes don't work, then the BTC is released back to the seller.
Same situation goes for moneypaks and have done this process a couple times using escrow for said moneypak trades. Good luck to you OP.
That's exactly what I have been saying in the PM's. Thanks.