Also, the actual items being sold were "mystery" gifts, not actual items.
My guess is that paypal views this as high risk because someone is sending money to OP, and OP is sending "something" to someone else. It's not trackable through PayPal's system, which means there is a high potential for chargebacks, which cost PayPal (and everyone else involved) money.
This seems like an extremely reasonable freeze to me, especially given that the PayPal rep told OP exactly what OP could do to sell these items: ship to the actual buyer and tell them what they are getting, and do so under a different name than your original attempt. That's kind of the only way it can work.
OP's situation is pretty weird. If that conversation actually occurred, it wasn't handled well at all, and PayPal may well have done a lot wrong here. That doesn't mean it wasn't a high risk situation when PayPal initially froze the account to stop it from getting riskier.
I also think the OP's wrong about losing fees on everything twice even though the payments were refunded. When you refund something through PayPal, PayPal refunds its fees to you, even if it was a credit card transaction.
Even if that was indeed the case, a simple investigation of the issue would have cleared things up. Businesses are supposed to work with customers, not fuck them over at the first sign of trouble.
I hate to come down on the side of Paypal, but it would be so easy to abuse the donation button by doing exactly this, and not sending out any gifts. There is no way paypal can test this.
(I actually spent a half hour talking to my PayPal account manager today about this very subject, presenting different charges and asking why fees were or were not kept in various situations; however, I do use micropayments, so my results are not going to be terribly relevant, and we are actually continuing the conversation tomorrow. ;P)
Note that I'm not saying this is the case here, but this is the risk from the payment processor's standpoint.