Nice set of readings Marc but which refrigerant

Can you get a set of oil pressure readings at all?

Other than that I suppose you could pump down the compressor and pull the drain/level plug to measure how much is in there. Remember of course that some of it will be around the system.

The other thing is that it is normally the refrigerant that keeps the motor cool, if you are that short of oil you could be getting close to seizure.