ad 2.)
Unless you specify a seperate log file for firefly, firefly logs to syslog, which is located in
/var/log/messages
You might find
tail -f /var/log/messageshandy
ad 3.)
If playlists are present, but cant find any songs, chances are the path to the files are no longer correct.
You need unix-friendly path names, and relative path names in your m3u playlists.
Which program did you use to create your playlists?