I easily found and scanned in ...125W, ...
...
So I'm ready to move forward with the motor.
To already get an indication of the offset angle of the dish, you could measure the dish face angle while fixed at 125W!
(Elevation angle towards the satellite is 33.23, so practically the same as to due south.)
That could help for your uncertainties about the dish elevation scale.
Keep up your research. If not you, who?
You are a flatterer!

I recently managed to develop an
exact multifeed skew angle calculation method, which was really a challenge. It needed to incorporate three elaborate angle calculations; which took me quite some time to think through. I still have to put the calculations in a spreadsheet, and test them in practice.
Apart from that, I want to finish a bunch of (new) equations for measuring and calculating the geometry of parabolic dishes, no matter if prime focus, offset, or multifeed dishes.
For the modified motor angles, there are practical methods already, that are about accurate enough, I would say. So though theoretically very interesting, not a real priority for me.
Same is valid for a calculator for designing the actuator triangle and the zone of maximum precision, etc. I find there seems to be not much interest in that subject (as there was not much interest for USALS-like calculations of actuator lengths, and pulse counts, for actuator setups)....
I like to use my brains for analyzing such problems, though!
Succes with the next steps in setting up your motor,
greetz,
A33.