1st Question: I only know two sites; accounts.net and toonstorm. I went to both and they told me the name has to be the same on the paypal account/WoW account. If it's not, they will not accept the account.
2nd Question: The best way to keep it safe is buying all three keys, make an account using the same last name as the previous account and transferring off the characters to the clean account. Than ban the old account.