Not having read every post in this thread in intimate detail... my input regards getting the machine set to Auto mode.
I went and checked my own Dreamstation Auto CPAP (500X150) late this afternoon and took some pics that may help.
To enter clinician mode push the round button in, and the ramp button at the same time.. hold them for 5 seconds and the machine should then access the clinicians mode.
Once there look for the Therapy box and open it.
You will then see 4 boxes, CPAP - A Trial - Ez Start- cmH20
Select the CPAP box.
Rotate the knob to the Auto setting in the CPAP box and press the button again to select Auto mode.
I believe this should have your machine in Auto, then you should be able to set minimum and maximum pressures based on the figures that were found to be optimal for you during your CPAP trial period.
This is not the same section where the machine is set in Trial mode.
I will add a rider to my information here and state that I have not actually put my machine back in to Auto at this stage, but my understanding from my clinician when I said I that I wanted to be able to put it back in to Auto mode at any time in the future was that I could do so.
Some time down the track I would be interested to see if I can put my machine in Trial mode, I suspect I would be able to do so.. based on the fact that the clinic uses rental machines to lend out for repeat trial periods of customer after customer multiple times per year.
(sorry for the odd sized pictures, I tried initially to add them as thumbnails, but even downloading them in the smallest size available from my phone they are still too large for what the forum will accept.. so I have tried to reduce the sizes by cropping them as best I can from my Photobucket account... my apologies)