Have you tried increasing the site /theme width?
Do the following so we can understand eachother.
Type grey in Main options > General Appearance > Outside BG color box. This will show you the outside of the site. To use that space you need to increase the theme width
type blue in Main options > General Appearance > Container Area >Container area BG box
Type yellow in Main Options > Content Area > Content Area BG color box
based on these color, post back as is and explain what space you are trying to eliminate
Also make sure to look at it on different browsers, in case you are seeing sometjing I don’t (I am looking with IE 11)