Learned Lesson with USPS Global Shipping Program

[Throttlesteer]

I'm about done with Ebay and especially the bogus Global Shipping program. I've had problems with 2 transactions (out of 10 or so) where the buyer never received the card. USPS still shows it in transit, but it never moves out of that state. The most recent, I have a buyer upset that his card didn't arrive in time for Christmas, even though it was sent USPS Priority through the GSP. It shouldn't take two weeks to go to Canada, but it is the holidays. He opened a case against me and is asking for a full refund. To top it off, I only charged $5 shipping but his invoice shows $26.18. Does the GSP charge the buyer a totally different amount than my own shipping costs?

I followed every Ebay guideline, but it looks like I'm going to get screwed again. Globegistics still shows the package in transit and was updated 12/20. He wanted the GSP shipping refunded and then just decided to go for the whole amount. To top it off, he has 4 feedback which sounds suspicious.

Should I wait for Ebay to resolve? Do I have any recourse with PayPal?