If getting the columns to line up is the main frustration, you can easily work around this by either adding a blank box on the dashboard to shim it, or even adjust the left header section of the % difference sheet farther to the right so the columns line up.
You could also consider adding a calculated field that simply contains the string value "Percent Difference" and placing it on your rows next to Month(Date). Then, adjust the left header section as John mentioned so that it lines up better with the worksheet above it on your dashboard.
Thanks to both of you for your help. I marked John's answer correct simply because it was the one I used.