If it's cancelled by ebay, fees are refunded automatically.
It makes no sense whatsoever that he would cancel the auction himself when 10 of the 15 boxes had been sold.
Since the auction was cancelled by someone, I agree that the previous wins are now null and void. You should only have to pay for the new auction you bid on.
Is it possible to file a claim for the previous boxes, then pay for the new ones? Although it would probably end up really making him angry.

He's violating ebay rules there somehow, so you're totaly in the right.
Oh,wait!!!! Also, did you get an email from ebay about the cancelled listing saying that you were not responsible for completing the transaction?
I've gotten one of those before when an auction I was bidding on was cancelled by ebay.