the GA pilot makes the request to fly up the river the controller, who
feels he is too busy, says ":Aircraft calling remain clear of my
airspace"
OK, so is the VFR corridor his airspace?
Well, according to my reading of the regs, NO...
He is not in control of the VFR airspace underneath the Class B...
The ruling issued by the FAA says, VFR aircraft must be in contact with
ATC...
He is in contact with ATC... As I read the FAR's the GA pilot says,
"Roger", dials up 1200 on his transponder, and continues on his tour of
NY...

That probably wouldn't "fly" with the FAA. I believe they've always
interpreted "two-way radio communications" to have been established
when the controller responds to your call by using your tail number.

Also, the exact text of the NOTAM states:

"...UNLESS AUTHORIZED AND BEING CONTROLLED BY ATC."

You are neither authorized nor being controlled in your example.

--
Guy