Thotbook consists of two websites, the homepage and the forum, because of that, all of your profile info is handled on the homepage, not on the forum. So in order to change your display name, login on the homepage, click your profile avatar, click Settings > Profile > Edit > Then change your Nickname. You may have to logout and login again for the changes to take affect. The settings page is also where you can change your email address.
Every day a new person asks to delete their account, it's annoying, and it's a lot of extra work that I don't have time for. As an alternative, you can change your nickname to something random, and you can register a quick protonmail.com account and change your email address to that random protonmail account and then forget your account details.