navigation issue

Unless I have settings wrong, I need to force the use of the off canvas menu for accountantswebdesign.us on all screens smaller than 1440 x 900.
The burger menu only appears by default on my phone, but all tablets and smaller desktop screens display the main navigation menu. Problem is, it is forced out of place down below the header. Even in landscape on my 12.9" ipad, the navigation is too wide for the screen.
Thanks