I'm working on 90s steel Dawes Street Cruiser that has a deep chip on the top tube exposing the frame beneath. Moisture and corrosion has made its way beneath the paint causing bumps (shown in the picture) in a 20mm patch.
I'd like to either get these out or reduce their height and seal the rust spot. 
I'm reluctant to expose the steel in such a large area but will do if it solves the problem. What's are my options? 
Thanks

[![Dawes Street Cruiser top tube rust][1]][1]


  [1]: https://i.sstatic.net/0NOPXyCY.jpg