Raising the minimum pressure may present a problem of discomfort in getting to sleep so the ramp may become your friend and EPR set at 3 will likely help also.
As has been mentioned, raising the minimum pressure slowly is normally best but if you can tolerate a larger jump, so much the better but if a large jump proves unsatisfactory, don't let that discourage you from going back to smaller changes. I found it remarkable that I was eventually able to tolerate higher minimums since when I first started I found 6 cm to be intolerable. Now I start at 8 cm and feel no discomfort at all, indeed I sometimes wonder if the machine is working! The fact is that exhaling under pressure actually makes the lungs work much more efficiently and that cancels out any perceived losses due to lesser volume.
I had troubles getting my AHI down when I had the starting pressure below 8 cm even though I use the S9 AutoSet. It just didn't have quick enough response when starting from a lower pressure and needing to get to 12 ~ 13 cm in order to handle the obstructions before they got scored.
By having obstructive events uniformly spaced from 30~45 minutes apart, you're playing into the weakness of the AutoSet machine and how it responds. Raising the minimum can work around that weakness.
Good luck with your quest for the proper setting. Do not give up! Trust me, you'll get it mastered in time and be well rewarded for your efforts.