Steve, I assume you downloaded a copy of the instructions for the Holland Steer Axle. You have model AS-120. The details of how to do the measurements are on Page 8, Fig. 7.
If not: measure the bottom of the frame rail to the ground (A). measure the center of the wheel to the ground (B). A-B = the air spring mounting height, which should be 262 mm (10.31"). If you can't get within 6mm of this you should get expert advice. I would not tamper with the linkage.
As for the difference in the 2 sides it is probably because they are loaded differently. Have you weighed your coach recently? I suspect you have a lot more weight on the driver's side.
John and Mary Knight
2015 Ventana 4311, 2015 Cadillac SRX