If only an ASW exercise, why under an active air corridor and why didn't the NTSB or FBI so state? ASW exercises are not considered secret, why this one? Are you going to tell us that the mystery back and forth flying craft was part of the ASW exercise and not a drone? Are you going to tell us that a P3 tows a magnetometer at 20,000 feet altitude? Get your story credible before springing it.
I was trying to make the point that your theory rests partially on the 30 knot target being a submarine, when there is no docmentary evidence to support that assertion. I don't know what the 30 knot target was, but it was just as likely a helicopter or a surface vessel as it was a submarine.
Absent the submarine or any military platform, your theory is inoperative. There being no evidence of either, your foundation is nothing more than the ground floor of a house of cards.