^That's a lot of text, too much for me, but I'll take it's a decent description of what to measure.
My TLDR (too long didn't read) summary would be that you need about 3 measurements.
Rim erd or the diameter of the rim
at the nipple seat.
The diameter of the circle of the holes in your hub flange.
The distance of that flange from either the centre of the hub/axle or from the face of the locknuts.
I would strongly recommend you measure these things youself and do not rely upon anyone elses measurements, even the manufacturers.
After that it's simply a case of plugging numbers into boxes.
I always use at least two calculators as a big difference in numbers is a great sign that you've entered something wrong somewhere. I really like
https://www.prowheelbuilder.com/spokelengthcalculator because if you enter the distance of the flange from the locknut it'll tell you the distance of that flange from the centre of the axle/hub or vice versa. Lock nut to flange is pretty easy to measure, the maths to work out centre to flange from that is not hard but the prowheelbuilder calculator does it for you.
I would say that measuring things and typing numbers into spoke calculators is the easy bit of wheelbuilding. If you are finding that a struggle then paying someone to build your wheels might be the better option.
