The new field can be added in the file theme.php. I can help you.
If you want, you can create a new user to me in your admin panel. In that way, I can modify the code on site. I have done this with other users and there were no problems. You can trust me. I only want fix this problem. You can send me the information to my email firstname.lastname@example.org
I don’t understand what you want to say about the feature with the subscribers.