I have some questions with respect to the calibration procedure. I have done the calibation with the attached router bit. This means that I have to raise the z Axis about 40mm. I guess this is not recommended, right? Another question is with respect to the output of the calibration process. There are the measured belt lengths printed. Does these lengths measurements include the Maslow_armLength and the Maslow_beltEndExtension? Are the lengths projected onto the 2D plane? This means, that is very important that the calibration is done without any router bit, right? If it is projected onto the 2D plane, are the Maslow_tlZ and so on used included into the Maslow.yaml?
That is right, the math assumes that the z-axis is lowered all the way down so your calibration won’t be precise.
That is exactly correct 
Yup!
It sounds to me like your understanding of how things work is already spot on 