Well, I’m not Nicol but if I may be allowed to interject just to say that, I guess I’m not on your wavelength at all. If you are working not only from a drawing but a detailed construction manual from an eminent horologist (John Wilding, CBE), why do you need to calculate anything??
The drawing clearly says 8.64″ dia. for the main wheel and to use a .75 module cutter, that’s good enough for me. I just don’t see why I would want to carry out any calculations when the information is there in front of me.
Similarly if I were building a locomotive to a reliable published design I would not feel that I would need to calculate very many dimensions at all.