You can login via Tor with a browser in private browsing mode. That way your ip address and your paypal account is not involved at all. Login via Tor into Paypal is possible. If for whatever reasons it is not possible, consider me a fraud In doubt err on the side of the seller.

December was extreme, but if that case it happens again, I agreed on paying the fees. That will be part of the deal with the seller. In case #3 is not needed the seller will only sign transactions which include the 1% transaction to #3. In case #3 is needed #3 will only sign if their 1% transaction is included. I think it would even be safe to pay those 1% beforehand. But that is something which I would have to agree with the seller on. I mean the seller is using #3 as well and it should be find to pay #3 beforehand. In any case, #3 has not to worry about transaction fees.