Hi, a big thank you. Your error-spot looks to largely have fixed the fundamentals. It compiles and produces a PWM signal whose duty cycle changes as the pot is adjusted.
Alas, it's not without its issues. Using oscilloscope readings...
The voltage output (at hi state) is about 60% of that of the 30Hz design (and any other pin 9 design I've created). Not clear why.
Also the low state output signal has sine wave noise within it (about 2 cycles within each down state) - at about 20% of the hi state voltage (rather than a clean constant lo at 0v state). Again, not sure why.
I checked wiring and reloaded the 30Hz code just to compare and did not have either problem. Net, the LED no longer comes on at differing brightness levels. Strange, can't think of an obvious cause.
So massive progress but no quite there. I'll try a few code preset value adjustments and see what happens.