Andrew_S_C:
If anyone has a "set very low PWM frequency" known working code that still allows for a wide duty cycle variation within it, please let me know.
Blink Without Delay (and even good old Blink) does exactly that. Very low PWM frequency (by default 0.5 or 1 Hz), 50% duty cycle. Changing the on and off times gives you any duty cycle you need.