Harry...You've got it. Look at it like a lever and fulcrum. With a given load, you do the same work in lifting it. The location of the fulcrum determines how much force you have to exert in order to do the work.
The effect of the small radius/reduced advantage comes immediately...starting to fight the slide the instant it starts to move. Think of it like stabbing the brake pedal momentarily as you stomp the go pedal when the light turns green.
Greg...Your firing pin stop geometry is intended to increase the mechanical advantage in overcoming the hammer mass and mainspring load by placing contact high on the hammer...exactly the opposite of what the small radius accomplishes. I took Browning's small radius a little further and made it a little smaller in order to reduce the mechanical advantage, STI went in the opposite direction.
It's done to insure a strong cycle rearward with calibers or load levels that don't generate enough oomph to drive the slide. Your 9mm is one of those. I've done it myself with that .45 pistol that I set up for my daughter for use with powderpuff loads...around 600 fps with a 200-grain bullet.
As far as your issue with the disconnect, about all you can do is make sure the bottom of the stop is flush with the rail, and maybe do a light bevel.