As for par-3 holes under 100 yards, I have seen VERY few such holes on regulation 18-hole courses. I think I've seen 1100 courses overall, and can only remember a handful that were really less than 100 yards from the back tee.
George Thomas had one at La Cumbre that he illustrated in his book, but it's gone now.
I am not positive it was under 100 yards from all the way back, but the one that stands out the most in my memory is the 17th hole at Conwy GC in Wales. The previous hole is a very long par-3, and then the 17th is very very short [though not easy]. The official names of the two holes on the scorecard are, for the long hole, "O.L." and then for the shortie, "L.O."