How do I change the developer's email that a new user gets when they sign-up for my site? See image below..
Will I have to completely set up a new firebase account with a different email address and change all the code corresponding with this one? Or is there another way?
If I'm understanding you correctly, you want your project to be associated with a different email, correct? If that's what you mean, then you can go to the Firebase console, click the gear>Users and Permissions, add the other email as the owner, accept the role with the other email, and then delete the original email you no longer want to associate.