When you Block an ID, in theory eBay will Block all IDs of that person.
It's not perfect, because one way they do it is by Blocking the person's online address. (I'm a technodolt and don't know the official name.)
One way to prevent games is to make all your Fixed Price listings, IMMEDIATE PAYMENT REQUIRED.
They will then stay open until someone actually pays.
Use tracking on all shipments. (Most US sellers do because USPS has such cheap tracking, but us foreignors often don't)
Look into the No Returns option. It may actually increase the number of Claims, but since the claimant is going to have to pay return shipping in most instances, it could discourage your PITA.
Report the PITA and keep reporting them. It's quite likely they already have a track record.
It does look as if the second mistake you made was in not Blocking the buyer after they left that first neg.
