Well up until very recently when the island platform went in service, (last year) that area on the westbound track, where in teh 1979 pic shows the "circle" there was a shelter there for folks to wait for the train - the whole side was a platform, all the way down to the former Augusta St. Xing (closed in 2002 i think it was), but up in that area was a bus shelter kinda thing, and i wouldn't be surprised if in the past, there was an actual small canapy structure there. I have never seen any pics of one tho.
The station building on the eastboudn side is the "NYandLB" station building - the NYandLB RR was jointly owned by the PRR and CNJ. That was the only station in South Amboy (downtown at least).
The building right next to the circle parking lot and John St., adjacent to the platform, was the former Raritan River RR headquarters I do believe.
That 1979 pic shows E units coming into town
great catch!