#1 What should be the correct height? None of the above. Its not tested that way. tire size , inflation, fender fit, measuring position etc. keep this from being an accurate measure. The idea in most MB height measurements (done with jigs) is to measure the relative compression of the suspention.
With all that said, we use your technique often to know where to look for driveability/alignment problems. We do alignments for a wide range of shops. We recently diagnosed a brand new Ford van that was being used for handicap transport. The weight of a lift situated more to the passenger side was their problem. We sent it back to the shop and they rebuilt the right rear leaf ( probably more than once) till they got the arch measurements right and we realigned it and the feedback is that the customers problem is gone (was to the dealer twice and two tire stores before it went to an independent specialist who brought it to us).
This example was given to answer #2 and #3. Other than starting with new springs there are no "right" answers. The right answer is the finished project. Unfortunately your heights indicate at least two problems (unlike the van). The fact that the front is higher on the right but lower in the rear is not good. Unfortunately to really get this right (from the cars standpoint) you need the heights right with the car sitting on scales all reading the proper relative weights.
The other point about your readings is that the front versus rear tell nothing with arch measurements. For basic trim I often measure the rocker moulding for levelness. The car should not be lower in the rear as they will get as they get older.
Owner 24 bay BSC
Bosch Master, ASE master L1
26 years MB technician
[This message has been edited by stevebfl (edited 03-19-2000).]