eBay refunds the fees IF you resolve the problem without them having to step in. There are exceptions but generally, once they step in the buyer will get refunded and your fees are forfeited.
In the May scenario, did you ask the buyer to repay you? If you are already in a transaction with them you can ask for their Paypal address and send them an invoice through PP.
"They stated tracking was not sufficient" - Does that mean that there wasn't delivery confirmation showing that the buyer had received the item?
When similar things have happened, I've contacted ebay for business on Facebook by sending them a private message with all of the information. The are fairly good to deal with there. You can also send them a message on ebay Twitter.