Revo would work fine
Backup the two files mentioned here (save them to the desktop)
You can only access passwords stored in [b]signons.sqlite [/b] if you have the correct [b]key3.db [/b] file that stores the encryption key needed to decrypt the names and passwords. If copying the two files to the current Firefox profile folder doesn't work then you may have a wrong key3.db file.
Make sure that you have copied the two files to the correct location with Firefox closed.
You can use this button to go to the Firefox profile folder:
•Help > Troubleshooting Information > Profile Directory: Show Folder