Aside from the other remedies, I would suggest switching to Firefox Portable, then you can create a couple of backup copies and number them with suffixes, as 'Firefox bkup 1', 'Firefox bkup 2'.
Then if everything gets hopelessly goofed on your active copy, export your bookmarks.html file to Desktop, rename a backup copy to be the active copy (temporarily rename the goofed copy 'Firefox goofed' before deleting it), then import your up-to-date bookmarks.html.
^re: [I thought "sneak snack snuk" was better but online reference says I should write "sneaked."]
You could also write or say 'snook'.