Hi
There is no calibration and the switches are not in the pedal assembly
The 2 micro switches on the brake valve are your problem
Firstly make sure you have the correct plug in the correct switch, I've seen so many people put the plugs round the wrong way.
Easy to monitor with a laptop or failing that consult the wiring diagram.
Obviously half depressed should activate first then full depressed. Remember the fully depressed switch is the one that allows the starter negative to engage the starter.
So if it starts at half depressed then the switches are wrong

The brake switches are out on adjustment, possibly an issue in the gearing section of the pedal assy that works the brake potentiometer, excessive play in the pedal shafts, etc.
You may need to recalibrate the brake pot with the service tool
The pedal "half depressed" signal is incorrect (T237)
The normally open and normally closed switches are not correct (T238)