I guess this is dead. The data is backed up but useless.

Is Gas Cubby Free still crashing? How did you take the backup? You can try forcing the .sqlite file in to the Paid version (but I cant promise sync will function properly afterwards)-
https://www.fuelly.com/forums/showthread.php?t=16945

I was having the same problem as OP. Turns out this was because I was using an encrypted backup, so iPhone Backup Extractor was extracting corrupted files. Instead use iExplorer (which can open encrypted backups, still need password though) to open the backup. Copy file from backup to iPhone all in iExplorer and you're good to go!