When using iTunes Backup or iCloud Backup, your Filmlog database is saved automatically on every synchronization. If you restore your device from one of these backups all your movies are just in place. In addition you can manually access your Filmlog database via iTunes > *Your Device* > File Sharing > Filmlog.
No. Filmlog is a personal diary and reference to movies their posters, facts, cast and crew.
Filmlog for Mac is coming soon.
Well, never say never—but it is very unlikely.