I’d suggest you to delte the # symbol from all tags. As long as you do not change the slug, all URLs remain the same and there’s no disadvantage. Then in the plugin settings activate the option “Add hash symbol to WordPress Tags” in the “Display Settings” tab. With this option activated all the tags will be displayed with a leading # symbol – assuming that your theme uses the WordPress standard functions to display tags. I’ve added this option exactly for such a case.
You safely can test this by just activating the option “Add hash symbol to WordPress Tags”. If everything works fine, you should see two # symbols. After that you can delete the # symbol from all tags and nothing changes for your visitors.
Please let me know if this solution is all right for you and if everything works.
Regards,
Peter