SLF here, please be gentle!
Too many pages, not enough time, but it seems to me that the MCAS is functioning solely on inputs about the attitude (AoA) of the airframe in one direction only. No attention appears to be paid to the position of the airframe in space - i.e. is altitude decreasing? AoA says nose is high but longitudinal gyro disagrees and says flight is level? Inertial Nav Systems have been around for a long time - back when I worked in the aviation industry. OK, that might be too expensive, but my yacht had a gyrocompass that cost about $100 as part of the autohelm. Why are these simple technologies not used for cross-checking of something mission critical like AoA? Before pushing the nose down, it would be helpful to know where it was pointing beforehand. And how could an automated system be allowed to drive the nose down while the altimeter shows altitude decreasing and acceleration increasing - the end result is inevitable!