RE: Crossovers.
I confess that I only read the first page of this thread, so my answer may be redundant.
I believe the original routing was as the holes were played in the 1916 Amateur. If I'm right about that, today's #6 was #3, 7 was 4, 4 was 5, 5 was 6 and 3 was 7. There are no crossovers in that sequence unless the "normal" championship tee box on today's #4 was there from Day One (I don't know, although I would guess not).
Even today, except when the VERY back tee boxes are used on #3, the walk from 5 green to 6 tee goes behind the third tee box - no crossover there except in USGA events.
It is true that the walk from the original 13th green to the 14th tee did not involve a cross over given the location of the original first hole.
Therefore, there are two crossovers today (2G/3T and 13G/14T) + a third one in USGA events (5G/6T).
I believe the original number was zero.