I have a free account as well.

1) Go into settings and in the first tab, Global Options, you will see an import and export button. Clicking export creates a clipboard entry for all your settings, except the custom images as noted when you are doing it. After you uninstall and install you simply click the import button and paste what you copied into the box that opens up. I would also suggest you go into the Eversync tab and sync the dials and/or bookmarks. Since you have a free account you aren't able to do a full backup. What I also did was make sure all my settings in Firefox were how I wanted them so I could refer back to that if needed because I think a few of the settings didn't come back quite how I had them, After reinstalling all of my custom images came back because I have everything synced.

2) I only uninstalled and re-installed FVD Speed Dial

I was having the same issue and do use the sync feature. I uninstalled the extension, re-installed, and restored my dials backup and everything worked again. After restoring all of my other settings it still worked