The major manufacturers based in the US are left alone during most of the certification these days. I think it will be determined the failures are that of internal oversight at Boeing and FAA oversight of Boeing. I have done the MCAS training module online and it is really a poorly covered topic with no definitive actions. The Airbus I flew all had triple redundancy in the Alpha Protection System. I am sure that redundancy has save the day many times.
Yes, this. Last person I knew with one, it was quite visible and he did feel it act when he had arrhythmia. It was not a defib, just a pacemaker. I guess when things get out of sync, you can feel it.