Tu
The system was fired due to one single input from a quietly failed sensor without any checks, redundancy, whatever in place to keep it from happening
Quietly failed? The vane was wildly out of alignment with the shaft it rotates. The result was chaos.
I too am an old guy with far too much time on my hands. I read every post, some many times, in that two intensive years.
The replacement of the nearly new sensor with a refurbished one from somewhere in Florida still leaves me stunned. It's exactly the kind of trap fault-finders fall in to. It's vital to assume the new part might also be faulty, though the aviation industry is unlikely to provides time for a test flight for such a small part. Again, I question what was in the minds of the first crew and technicians in those first two days? Remember, it followed a grievously under-played emergency from the day before. In fairness, no one knew about the part's 'chaotic' status, simply because it didn't fall into that catagory yet.
The 707 nosing up at the late stages of a stall sounds related to the reason for MCAS. However, despite routinely reading duff gen about the reason MCAS was introduced, I only know about the inability to certify the MAX while nacelle lift was making the late stages of pulling back much too light on the pole. This was nearing the stall, and in certain turns - the latter being vitally important to get right.