Not 'heading' in my book. By the way, I'm puzzled why do you not view water as a liquid? "Cannot agree with any of that."
Debris orientation/position at 4000m will be governed only by the currents and the 'flying'/break off motion of individual separate parts and there will be a ZERO effect of any motion vector at impact. All bits will come to a pretty abrupt halt at immersion. Water is hard at that speed. As said, separated engines will go pretty much straight down. The fin/seat cushions etc float. Plot all points between?