Ebay Buyer Not Paying And Other Issues

I am seeking advice for a frustrating situation that is currently ongoing.

A buyer won one of my lots through the "best offer" feature. It has been two days and he has not yet paid.

I sent an invoice yesterday reminding the buyer to pay. The response I obtained from the buyer was that he was "having trouble with Paypal and pay as soon as it is repaired."

A couple of questions, as I prepare for a couple of possible scenarios:

1) My ebay store is currently set up to automatically open a case on the 4th day of item not being paid. I've never had to use this option, because most (but not all) my listings do require instant payment. How much communication does ebay expect me to pursue with the buyer before an unpaid case is opened? Does ebay expect the seller to be lenient with what seem to be implausible excuses?

2) What should I do if the buyer contacts me in a few days telling me that he does not have the means to pay and wants me to reduce the price or cancel the order? If I cancel, ebay still charges me listing fees (quite high for the item in question), and I am still prone to negative feedback. On the other hand, if I somehow force the sale through, I have a feeling that the buyer might find some excuse to trigger a refund process via ebay. I guess my question is, does ebay have a system in place to refund final value fees when the buyer requests cancellation? The vagueness of ebay's criterion "you and the buyer agree to cancel the transaction" is something I hope to elucidate.

3) I have good reason to believe that the buyer operates at least two different accounts. Is this common at all, or is this something to be concerned about?