Mobile breakpoint

I want the left sidebar menu to disappear (and show the mobile menu) as soon as the widget areas begin stacking. However the breakpoint seems to come too late, so on a tablet the very large menu appears above the other widget areas and the main page content. How do I fix this?

There is a password to view the site which I can provide. Also I’m not sure this is the place to post pro support questions.

The page I need help with: [log in to see the link]