The private key is the only way to get access to your bitcoins. Either you have the 12 words passphrase to restore, or impossible. Bitcoin encryption is known for being extremely robust.
You should be able to make any adjustments to the printing order in the Print Options window. I'm not sure if this particular change is possible though as it depends...
Of course you can cancel the sale. You are under no legal obligation to carry on with any sale right up to the point where a contract is signed, especially...