Hi there, Unfortunately, we cannot save your jack-o-lanters if you re-isntall windows.

Brand Thunder does not individually track users, so we cannot save your data if you format your hard drive.

Here's why...
when you re-install your windows os, you are probably reformatting your hard drive. When you do this, you lose all your data, unless you back it up.

Firefox saves its data on the users hard drive, so if you want to save your firefox settings (which include canvas, and your backgrounds), you must back up your firefox directory.

Please Refer to the following article on how to back up your profile data.
You have to do this if you are going to reinstall windows.
Backing up your information

As for the highligher add-on, please go on mozilla addons and try searching for an add-on that provides this functionality. Currently Brand Thunder does not make such a feature for firefox.