Hi Ciderdrinker,
I had seen the baptism you mention, my concern about John Fergusson was that there are other Fergusson marriage records at Athelstaneford, 1700 - 1735,both in 1712 for a Jenet and an Isobel where he is a witness, also a James in 1731, his witness is Archbald Fergusson.
I was hoping the original record on SP may help. Sadly no Kirk Session records there.
Colin