Page Layouts and Wasted White Space and Dynamic Resizing

Hi Ryan - Thanks for the response. 

The standards are laptop resolution (1366x768) and External Monitors (1680x1050). 
The exceptions are usually department related (3347x1050) (or more). 

The issue is, we migrated their sites from Server1 to Server 2 (upgrading from 2013 to 2016) and the new Server / Site has a different template in place. The Site Owners/users have sites developed that were migrated that have fairly wide and informative middle column displays (their old site didn't utilize the right column). Now, with the new template, utilizing the right column, their main content display area is reduced from a possible:
 - External Monitor (1650px width): 1400+px to now a maximum of 650px (reduction of over 50%)

 - Laptop Monitor (1366px width): 1130+px to now a maximum of 650px  (nearly a 50% reduction)

I'm trying to find a way to maximum the main content column (understanding that this isn't going to be perfect for every page, every site, etc.) The standard template layout is shown to right. 

From my analysis, the template appears to have loads of wasted white space as you can see below:

I'm putting forth my recommendation for the layout (keeping the format in place). But as you can see...there's a LOT of wasted space. A LOT! And ideally, I'd be able to set a minimum width of the Centre Column (ie. 800px). 

Any recommendations, suggestions, ideas? And again, I appreciate, no single design will appease every use, every layout/design. But, if I can minimize the wasted white space, I can give them a little more flexibility and area for content on their pages.

Cheers.