Apologies, but there are no options for changing the widths of columns of sidebar layouts. These are CSS customizations you’ll need to make to the theme. All of these styles can be found at the top of /framework/frontend/assets/css/themeblvd.css if you’d like to copy any of them to your Child theme to modify and override. It’s all percentage-based and this how everything remains responsive no matter what the widths of the surrounding containers are.
For CSS changes, it’s a good idea to use a tool like firebug or Google Chrome’s built-in developer tools to locate them and then put the edits either in your child theme or in the “Custom CSS” option on your theme options page.
Also, here’s a helpful tutorial on how to use Firebug – http://vimeo.com/20917974. The only thing I’d suggest not doing is actually making edits to the theme’s CSS files, as it shows at the end of that video. However, the video serves as a good introduction to Firebug and how it can be used to find what CSS is effecting certain areas of your site without ever digging around in any files.