Re: Red knob next to the parking brake lever
It looks like the same knob and cable used to adjust the gas/air mixture at altitude in a piston aircraft. If you twist the black knob surrounding the button, you should be able to make fine adjustments to the setting. Pushing the red button unlocks the vernier and lets you make major changes by pushing or pulling on the knob.
These controls have been used by others as a poor man's cruise control, holding the pedal to the metal on long stretches of interstate highway. It would especially be desirable with engines like a DT360 that barely maintains speed (if it can) at full throttle. Anyone trying this trick has got to train their mind to remember to smash the red button to the dash in a panic stop, as the engine is not going to drop to idle when you touch the brakes like a cruise control disengaging would.
I can't help you with the brakes.
Someone said "Making good decisions comes from experience, experience comes from bad decisions." I say there are three kinds of people: those who learn from their mistakes, those who learn from the mistakes of others, and those who never learn.