I don't have any assistance to offer, but I will say that I just this past weekend got the rear suspension to budge after a few years of an *occasional* try at it. The room you have to work with, that weird-ass wrench, and the stiffness of the spring all conspire against you.
As to your desired settings...it's up to individual preferences, and as you say, how heavy te load. I like a little stiffer ride, and keep the air in my car tires a little higher than recommended. But my friend has a Jeep which I think offers a miserable ride, while she is looking to replace it with another one.