OK, now that you are seeing how it works I'll tell you the trick. Shame it will go to the archives. I'm sure a bushel basket of systems are going to get screwed with as a result.
First thing, I think you are probably doing alright unless its a lot colder where you are. You probably won't get heat except in defrost with the temp higher than the temp wheel setting. Also shut-off the compressor if you wish more heat.
The whole point is that the magitude of the cooling or heating attempt (by the system) is a result of the combined temp sensor values as opposed to the setting you have given. AND, that is where the secret lies. If you take a flashlight and look very closely on the right side of the temp wheel there is a white toothed gear about the diameter of a nickel. It is the positioning adjustment for the temp wheel. If you want it colder run the degree wheel in the direction of cold and then take a tool and continue the gear in the same direction. Opposite for heat.
The proper tool I have used is a thick feeler gauge cut with a saw tooth pattern on the edge. Cut the teeth with a carbide wheel and try to match at least one or two to the distance of the gears spacing. To view this the temp wheel must be pushed to the side and nothing needs be disassembled. Get up close.
Bosch Master, ASE Master, L1
33 years MB technician