It looks like the theme is doing something weird; I can tell that the plugin is running fine because it’s loading its stylesheet.
But since you’re using a theme from the .org repo, I checked its code and it isn’t doing anything weird.
So there are two potential issues: either there’s a conflict with your footnotes plugin, or something was corrupted in either the theme or the plugin files. You can try temporarily disabling the footnotes plugin to see if that’s the issue, and if that isn’t it, I’d recommend downloading and installing a fresh version of the theme and plugin.
You would want to use a child theme if you want to use the manual-output code, and it would go in single.php for posts.
OR
Make sure all of the QuickShare config settings are set up to display QuickShare where you want it.