IT'S ALIVE! IT'S ALIIIIIIIIIVE! I was able to get the front element off just as you instructed, bathed both the fronts and backs of the aperture blades with lighter fluid, and lo and behold, even the PAD button is springing the leaves back to life again! Thanks, Yashinoff!
Oops, I spoke too soon. The lens is stopping down to the smallest aperture when the button is pressed, regardless of the f-stop set on the ring.