I'm not sure I followed your steps, but regarding your last question, yes the .mbl file is what points to the audio files on your system. The .mbl IS your library, the database containing all the info about your collection. It does NOT contain any settings. Library settings have a file that should be in the same directory as the .mbl file, and all other settings are in the appdata folder. For the portable version, that's a subfolder of your installation directory. Otherwise it's your %User%/AppData folder.
One thing this means is that if you reinstall MusicBee in some new directory (or on a new system), you can take an existing .mbl file and overwrite the one created on installation. If you're not intentionally maintaining multiple libraries, I would delete any extra .mbl files, so there's never any confusion which one is the right one.