A standard main wing stall followed by a deep stall condition
suffered by T tailed airplanes would explain the 30 degree pitch up and subsequent pitch down.
Airflow across the Horizontal stabalizer gets disrupted by the wake of turbulent air from the stalling main wing -due to the T tailed design the horizontal stabalizer is right in the line of fire.This severly limits elevator control.Recovery is only possible by trying to induce an oscillation or rocking pendulum effect, effectively having to let the nose pitch or "swing" up to the extreme of the envelope before it can swing nose down -just like a pendulum.These types of stalls are noted in the article below to be extremely difficult to recover from
deep stall:
Stall (flight) - Wikipedia, the free encyclopedia
In this hypothetical situation the question is -what caused the main wing to stall in the first place ?
1 Why the lack of speed ?
2 Was there an engine problem or maybe an inaccurate airspeed indication?
3 Was ice creating extra drag and if so how come the FDR shows
the autopilot did not trim to compensate?
4 Surely the above scenario looks more likely than a tail plane stall
as according to the NASA icing video a severe pitch down would have
occured first in that scenario?