agree on heat gun. I always try least invasive approach and work my way up. Maybe try a plastic scraper before the razor blade. I used plastic scraper and heat gun on my numbers, worked well. there are lots of glue removals at HD (some are citrus based) that may help remove residual glue. you can always work your way up to a wheel, and more aggressive approaches. I have also heard (but have not tried)WD 40 to remove residual glue. I just used it to remove some 4000 that was left on my boat after a project..it was only a few hours old, but came right off.
just some thoughts