Really delighted that you've managed to increase your sleeping time ... as you say with due pride RESULT!! +1!!! WELL DONE!!
One of the issues I was having was that when the mask leaks the CPAP machine increases the pressure to compensate, to the point where the pressure hits 19-20 and almost blows the mask off my face. Last night I dropped the max pressure to 15 (probably not supposed to fiddle, but my next appointment is a month away so I've got time to experiment), and that seemed to make a difference. I'm thinking I'll keep it like that for a few nights to get used to everything and then try it at 20 again. The AHI last night was either 15 or 18 (didn't have my glasses on!) which is better than my usual 70, but not good enough. I'm guessing that might be down to 15 not being high enough, but it still seems like good progress.
OUCH! I understand exactly what you're trying to achieve, but you really must give the mask a chance to work ... I'd suggest you start by refitting it!
You may have it too tight or not tight enough in the right places! Lie down with your machine OFF, with the mask slack. Tighten the bottom pair of straps then the top pair so the mask sits against your face but not pushing down on it. Each of the straps should be reasonably equal in length so pull the them gently away from the centre line of your face - think of your nose as the centre line! - until they are of equal length and then fasten them. Now 'fill up any slack' between your mask and your forehead by turning the dial - I think anticlockwise - until you're comfy. Now turn on your mask and see how it feels ... it should sit against your face a bit like the skirt of a hovercraft on the water.
I too started tinkering with my pressure to try to lower my AHIs ... but you are dropping your pressure settings far too far. You need to work very slowly if you are going down this route ... ie 0.2 drop and wait a week etc. But I really don't recommend it. The max pressure is set for a reason, and I would strongly go back to your clinic because although 18 is a vast improvement on 70, it is still far too high and this shows that the treatment is not correctly set to your needs. GO BACK TO YOUR DOC - but put the pressure back to the amount it was set at by the clinic, then wait at least a week so that the data concerning your pressure and AHIs will be useful to the clinic.
I know it's tempting but this is FAR TOO SOON in your management of the condition to be tinkering with your pressures and settings because you need to get baseline data before you try to alter it. And this data can't be based on just one night's settings. SORRY!!
Another question ... I normally sleep with one pillow, but I found last night was more comfortable with two however it does bend my neck up more (obviously) which in turn might compress my throat, causing / increasing Apnoeas maybe?
Pillow comfort is really personal and I don't feel I'd like to comment on it. I find that too high a pillow is uncomfy, but my old pillow feels more like a sack of cement, so it's really a matter of personal taste.
Please do persevere with your treatment ... and go back to the clinic to get your settings reviewed. There may be other 'features' available on your machine that might help you - that have not been used yet - and they might be the way forward rather than tinkering with the actual pressures going through the machine.