Does Mozilla have any back up of my bookmarks etc. ?

Have you synced your data with Mozilla account?

I have this on, couldn't find anything else

Right, but Sync could be cleared for various reasons. I'm afraid that we only do local backups.

I know this will not help now, but that is exactly why I use a password keeper separate from whatever browser I am using, including FF. My password keeper is a separate app that backs everything up to it's own "vault". (I also like that it requires its own password, which is double protection for sensitive info.) If something goes wrong with my browser, my passwords (and other information) are not impacted. Yes, I learned this the hard way.

As for your current situation, your passwords may come back on restart or reinstall. Something you could try first is to open another browser and ask it to import passwords from FF. I am not a programmer or a computer whiz, but I have decades of muddling my way out of weird computer events. It surprises me how often they work. Good luck.