Can not speak on much of what you need help with. One thing I will say, Z offset will change when layer height changes. What is correct for .1 is not correct for .2 ...3. .4 etc Again I have different machine, Different firmware and no Btouch. My process is set M206 to known value, mechanically set offset with feeler gauge, heat bed to temp I will use (Z offset changes as bed temp changes) and print test square. Adjust M206 so test square is .02mm shorter than the model. Wish I could just tell the thing to check and set with btouch but not worth the effort at this point. Good luck