Your fees (except the PayPal portion) will not be refunded.
If you want to recoup them just give the buyer a smaller refund.
One question; why do you feel you must refund the extra postage? Is it a huge amount? There's more to the cost of shipping than just the postage. The buyer paid what you asked for, unless they expressed some concern about the amount they were charged I don't see the need to refund anything. Prersumably you made a profit on the item itself I don't imagine you would refund any part of that.

"What else could I do? I had no trade so I became a peddler" - Lazarus Greenberg 1915
- answering Trolls is voluntary, my policy is not to participate.