One small point - my understanding, based on the testimony at the NTSB public hearing, (lots of good background info in the video archive from day 1) is that the selecting the REF SPEEDS switch to INCR only affects the stick shaker. It does not affect the stick pusher.
As I understand it the stall protection system (SPS) measures actual AOA against preset values for both shaker (imminent stall AOA) and pusher (actual stall AOA) activation. The SPS has no way of knowing if there has been an actual aerodynamic stall other than by comparing the actual AOA with the preset value, nor of actual ice accumulation on the wings. The INCR speeds switch lowers the preset AOA value to simulate the effect of ice contamination. I understand that this preset value is lowered for both the shaker and pusher, but perhaps someone with better access to the relevant documentation could confirm this one way or the other.