DozyWannabee, I note that takata's recent note about the plane aimed down when the PF requested NU and your comments about not seeing a conflict in that suggests another basic rule for "strange situations" such as the sudden drop to ALT 2 with no airspeed indication: Don't Play With The Throttles, Bunky.
The moment arm with the engines and their thrust do exactly the opposite of what you think you want. If you are thinking overspeed pull up. But don't drop the throttle. That will nose you down. If you are thinking stall, don't goose the throttle. That will tilt you up and slow you down. So don't play with the throttle.
But, for that matter, don't change anything except roll. Maintain pitch, don't touch the silly throttle, and keep the wings more or less level but fanaticism about it doesn't pay. Watch the altimeter. If it start changing rapidly aim the plane "slightly" to compensate. But don't play with the throttle except for VERY small nudges.