From what I've read on ebay.com, the buyer loses buyer protection by refusing the package. They can't file a not as described dispute if they never took possession of the item.
You can't get reimbursed shipping from ebay because you didn't pay ebay. You paid UPS and they shipped it. They're not charging you for the return so essentially that was free.
When you get the item back, reimburse the purchase price only, if the item was listed with separate shipping.
It is the buyer's responsibility to pay custom fees. Do not give them any money. If they leave negative feedback, do a follow up and state something like the buyer refused to pay custom fees & refused the package.
Add the buyer to your blocked bidders list.
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Non payers should get unpaid item strikes and be added to block bidders lists. Period.