(1) I would imagine that the definition of aquaplaning would be when the wheel rotation rate is less than the rate of aircraft forward movement.
I would very much doubt that aquaplaning took place, I'm 99% sure that the wheel would have been rotating, so I think the engineers description is technically incorrect.
(2) If engines have been shut down and the N1 rotation is merely due to wind flow, I don't believe there can be any noticeable thrust from the engine.
(3) Re chocking and releasing brakes....if you're going to chock the aircraft do it properly, with sufficient number and quality of chocks to hold the aircraft in position in case the brake accumulator is depleted / brake fails etc!
Why you would want to routinely release the parking brake is beyond me - the name of the device says what it is for - to PARK. In that I agree with Boeing. In my company we used to release the brakes when parked but imho properly stopped that procedure about 16 years ago. WHat is the downside - the chance of a stuck brake unit - not known that happen to an extent that it has prevented pushback.