The only way to do this successfully would be to use the @media queries and set up conditional blocks of styles that will apply in different media environments. For example by adding...
@media all and (min-width: 1200px) and (max-width: 1400px) {
#region-pre { width: 25%;}
}
so that when a screen resolution changes so does the theme. This method of course would mean you would have to re-style the whole theme for different screen resolutions and adjust the % width of the various elements of the page, which for this theme is not easy, but can be done if you understand how the page is designed.
Mary