You bet I did! My stylesheet is probably a mess, compared to some. Thanks for your thoughts, Mike Orange.
BTW, Hueman’s Theme Options panel allows the designer to choose “Always show sidebars,” even on low res devices, so that is how I lost the navigation & sidebar toggles. Obviously, I chose that setting because my graphics-laden sidebar is my navigation menu, so I wanted it to display at all times.
I think I will try using the WPTouch Mobile Plugin to make a separate mobile version of the site, instead of tweaking the Hueman theme any further and relying on its responsive layout for mobile visitors.
Thanks again.