In my experience, a total stoppage of the keyboard after changing mappings was caused by accidentally using the same scancode twice. I'd check carefully through the rest of the file and make sure 29 (or any other scancode for that matter) isn't also mapped to something else. If any code is used more than once, the external keyboard simply will stop working until you fix the file.
Beyond that, I haven't had success with getting the control key to work. We may both just be missing something simple. A more definitive source is
It gets into the kcm files as well as modifiers for the control key. I haven't experimented enough to see what might work for our little device.
Good luck! If I do get something working I'll let you know.