docboss:
First of all, welcome to the Forum for the world's finest pocket pistol.
With regard to the grip, I also can get, as you say, 1-1/2 fingers on the grip -- my middle and right ring finger, with the little finger supporting the pistol under the magazine. I have no difficulty shooting and controlling my R9 with one hand, and I am missing the first digit of my right ring finger (the result of some "unpleasantness" in which I emerged as the winner long ago and far away). I do not use a magazine extension, although some owners with larger hands find them useful. With the caveat that felt recoil is highly subjective, I would rate that of the R9 as less than J-frame with .38+ and certainly much less than with .357 Magnum. I have not cared even to try the PM9, Nano, and DB9.
I hope this is helpful. And, again, welcome to the Forum.