Max pressure for the rear shock is 43 psi. Manual gives a usable range of 0 to 43 psi.
I think the damper adjustment may slightly lower ride height, but at the risk of bottoming out on harder bumps. I couldn't use lower than '3' without hitting bottom, which is very dangerous.
Playing with air pressure and damper settings may allow using the lower damper settings. But you have to be careful in finding out.