How did that happen? When you say you have a backup but can't be restored, then something seriously drastic has happened to the code, I would suspect. Use something like phpMyAdmin to extract whatever you can that's not corrupted. This allows you to work with a clear view of the database tables and you can extract individual tables via the interface. Don't get me wrong, there are some advantages to using binlog2sql but I have found the visual structure of the data supplied by phpMyAdmin to be considerably more useful.
Best bet, once you have what you can get, dump everything, delete everything, database, code, all the directories and everything else. Create a vanilla install of your Moodle, maybe even a newer version, but not too new, too far from your current install, replace the database with your backup. That should get you off the hook. If you have time, then you may be able to insert the recovered data before you restore the database, again via phpMyAdmin. Good luck.
Best bet, once you have what you can get, dump everything, delete everything, database, code, all the directories and everything else. Create a vanilla install of your Moodle, maybe even a newer version, but not too new, too far from your current install, replace the database with your backup. That should get you off the hook. If you have time, then you may be able to insert the recovered data before you restore the database, again via phpMyAdmin. Good luck.