It's awsome that you explain in such a good way, alot easier to help then.
If the guy doesn't have your last name, he wont be able to recall the account he will need Secret answer and Full name for that, even if he did you could call Blizzard telling them that the hacked figured out your last name and he keeps recalling the account. You also said in the end that you're thinking about buying a new copy of World of Warcraft and The Burning Crusade, that will cost you a few dollars but if you're up for that what you should do is transfer your character to account2 and get account1 banned.
But just remember the guy you traded with can't recall the account by having the CD-Key only, he'll need the Full Name and Secret Answer.
I hope this helps you abit, wait alittle longer and you'll have loads of other tips.
- Cyber Jesus