So you deleted your Facebook application? Once that's done, you'd need to create a new application and get new API/Secret keys for JFBConnect. Any users returning to your site would need to re-approve your Facebook application, but their Joomla account would still be intact, so they wouldn't notice a huge difference.
Please let us know if there's something we're missing. It seems like simply starting over, in a way, will get you back on track.
Good luck!