Am I reading the flang to locknut measurements properly?

Go from the center. Make your own sketch, get the old/2. Take offset and then ftf. Inner/middle/center of the flange does not make a difference, you could calc both and see of spoke length changes.

I get 48 mm from centerline of the right flange to the locknut, or 46.4 mm from the right (outboard) surface of the flange to the locknut.

But I hate stacking up dimensions, there are tolerances on some of them and the errors can stack up, too. So take my measurements as “theoretical” or “nominal”

And the left side is 31.5 mm (to left surface of flange, or 33.1 mm to flange centerline)