The technical term for your buyer is 'deadbeat'.
You've done everything right.
Since you have already opened the Unpaid Item Dispute, four days later (96 hours) you can close it.
You are then released from the transaction and can relist. I know that is a disappointment.
You get your selling fees back and the deadbeat gets a Strike which makes it harder for him to bid and buy on eBay in future.
He cannot leave feedback for you. Good thing, too.
You can also go to your Seller Preferences and put an automatic Block on bidders with UID Strikes.
There are some other useful Blocks available there.
EBay does give time for real buyers to pay, since like many sellers they are not hanging over their computers every day, but eight days is enough.
BTW, eBay invoices your customer for you, if you included shipping information (and I hope you did). So one reminder that the purchase remains unpaid is enough to kickstart a slowpayer. Then go for the UID on Day Four.