I think this could be near the pinpoint location for a couple reasons?
First, I checked all the way down Valley Forge Rd using street view starting from the north part of his county. Nothing made any sense because there were too many trees and the road was too set back from the shoreline.
Secondly, beginning at Davis Hill Rd, on the left side still driving southbound, a large fenced area begins with no trespassing signs. The yellow arrow begins with the fence, and about 200 ft down there's a cluster of trees directly next to the dam's spillway (marked in purple). It would be logical if this section was part of his patrol to prevent trespassing on county property, especially by kids at night who climb on the dam. Given that he would have been driving south, the light from his left matches the location too.
One further thought regarding his odd description: any chance 'bywater' might have been slang/a misspeak for the dam's spillway? It's where high *water* *by*passes the dam? A byway for water. Irrelevant either their way, but it is curious how the spillway is directly next to this location about 200 feet down the fence.
Where he would be looking also does appear to intersect the approximate flight path of an aircraft going between Danbury Airport and the Bridgeport Airport. Short flight, so they would be smaller aircraft flying low.
Or, even more likely as others have suggested, it's a Sikorsky SAR helicopter doing training flights or testing new machines.
For example, this ^ is a Sikorsky at night coming in to land, and it does even produce the changing colour, pulsating effect like the officer described. The distance of the red and green nav lights from the white lights is sufficient to not be drowned out by glare. Unfortunately, if you go watch the full video, the lights are directional and forward-facing for landing. It wouldn't make sense to still be visible after it passed the officer.
As a note of intrest, when the spotlight is directly facing the camera in the video above, the glare makes the object look much larger. As soon as the direction changes, the light instantly becomes tiny, which could give the illusion of an object shrinking in size quickly. Especially if it was in response to him turning his spotlight on which could have alerted the helicopter pilots to avert there searchlight.
I wonder if there are any search and rescue helicopters that have a non-directional landing light set up for when the pilot is trying to light up the whole area underneath him while doing long line rescues, let's say over the ocean. Or any models that have search lights that are we facing (which wouldn't make sense to me, but who knows)
If someone wants to try match up the trees in the officer's video with Street View, then we could hopefully confirm with 100% certainty it's a match. I can't do that on mobile very well.