Hi Wbwlsaf,
Based on the result of your test, I doubt many would say you have OSA. You are in the clear on that one.
The RDI is the AHI + no of RERAs (respiratory effort related arousals). If you look at this video (about 5:30) it seems a number of studies have shown RERAs don't affect daytime alertness
https://www.youtube.com/watch?v=HCiPtQhN9uk
Whilst some "process-based" (cookie cutter) clinics may offer CPAP based on an RDI, others may be more sceptical.
You might want to have a look into UARS (that's what the video is about). As the video says there is no simple effective test for this available yet and an oximetry based test like Lofta is not of much use.
CPAP machines are very much designed to detect and react to OSA. They, and the clinics monitoring them, are all about the AHI. I've been on a CPAP machine for years with a low, treated AHI and still have daytime sleepiness. This does not cause any interest in a sleep clinic - they have done their job dispensing the CPAP and getting the AHI down. Once you have bought the CPAP machine and using it you may be deemed to be 'diagnosed OSA' (with all that in entails about fitness to drive etc) and have difficulty stopping it.
Whilst I understand they are useful for UARS, CPAP machines have not been designed specifically to treat it. Don't buy a CPAP machine in the hope it will magically deal with undiagnosed UARS.
Your list of conditions sounds dreadful to live with. My heart goes out to you and I fully understand your desire to find some way to deal with the crushing fatigue but, personally, I don't think, based on the study results, that CPAP is your path forward.
You mention a number of conditions which may be treated by fairly heavy medication. Have you considered drug interactions?
Best of luck finding some kind of relief.