Get one of the flight simulators such as MSFS or X-Plane. Take an 747 at the same speed that 800 was going, shut the engines off, give it full aft trim, and it will climb over 3000 feet, then stalls out and falls like a rock. These simulators are at least 90% accurate.
I doubt that "full aft trim" can simulate the decapitation and loss of the 80,000 lbs of the nose... It actually moved the center of gravity aft ward by about 13 feet while the center of lift remained centered on the wing. Nor can it simulate the sudden huge increase in drag caused by the aircraft suddenly presenting a 21 foot open fuselage and the resultant air hammer to a 400 MPH wind torquing the aircraft rapidly upward and backwards when the aerodynamic nose is suddenly removed.
In addition, your simulated aircraft, as you said, would stall out and "fall like a rock"... and splash in about 3000 - 4500 feet eastward of the point of the original initiating event because once it reach its Zoom climb peak altitude, it would have converted all of its forward momentum (exchanging velocity for altitude) and have close to zero left for eastward vectored movement.
But that's not where it splashed in.
The nose without any lifting surfaces splashed in approximately 1.1 Nautical miles from the point at which it is estimated it broke away from aircraft. It fell like a thrown brick (ballistically) and the 400 MPH effective headwind quickly decelerated the relatively lightweight nose. The main body of the aircraft, with a mass five times that of the nose, has greater momentum to spend against that headwind... and the main body fell ballistically 2.7 nautical miles from the initiating point.