Mark on "[Theme: SG Window] Change width of main content with side column"

My site is here. I'm having a real difficult time figuring out how to get a right column to work the way I need it. I've spent a couple of hours with the various Customize settings: Column sliders, checkboxes for right/left/full width - everything I could find that might have to do with column and content layout/widths.

Without a column (just the main content), the content area fills the page as expected, and I can get a right column (for a Facebook feed) on the home page, but I need that on the entire site. But even on the home page, I can't get the widths to change.

When you visit the site, you'll see that the home page has a right column, but the content area and the column don't fill the entire width (minus margins/padding on the sides). And that there is no right column on the rest of the site pages, but the width of the content area is real narrow, just like the home page.

How do I get the right column to show on the entire site, and to fill the entire content area?