Probably a small error on my part but for some reason the analogWrite is not cooperating. I have it marked in my code (*******HERE) and have debugged it and you can see my output seems to go through it with the output "Entered motorForward" and "Leaving motorForward" but does not seem that it writes it to the motorcontroller. I have checked my connections for PWMH and DIR and they are in the correct pins.
If you replace the motor controller with some LEDs, do the LEDs change brightness correctly?
The numbers you are using seem quite low. Is there a reason you are limiting the top end of the range to 78? Some motors won't even start moving until a certain PWM value is applied.