Just to point out your terms are unrealistic.

You cannot delete a BTCT account. The most that can be done is delete all the posts or the next best thing would be to change the password, then lock the account through the email you get.

Honestly I wouldn't get so bent out of shape over being called an alt, people are suspicious. This forum requires a certain thickness of skin that many seem to be lacking. I would remove money or accounts from the equation all together and make them wear something in their personal text or signature for a while.

Even if they accept the challenge as stated you left out 1 detail, a definitive deadline. They could say they are researching for years.