I reinstalled phpbb using the same files from the previous installation, did not link the main admin account, instead having the facebook account seperate and it's working fine for me now. Linking the main admin account rather than registering a new one didn't prompt me after with a facebook popup saying you are registered using the fb app.
And going along with ALIENQuake, could an option for auto-login be added for boards w/o email verification? My ISP doesn't allow outgoing mail, so emails are disabled throughout the board.
Another suggestion to integrate especially for people in my situation is whether email support could be added through the app using firstname.lastname@example.org
or something related as the sender, though I haven't received an email like that in a very long time. May have been removed?
Either way, thanks for your efforts and I will be keeping updated with this.
In attempt to clear up confusion with the connect button, I edited the image a bit and left a note above.
Feel free to use it in your forum, just add the line in domain.tld/phpbb3/styles/prosilver/template/index_body.html and login_body.html in the appropriate place.