I wish I had your time and stamina to post, but with limited time available, it's you who is settling for an arbitrary definition of death- whatever the best clinical practice of the moment says- and making it an absolute. I doubt if you'll find a medical professional who will be prepared to say that a clinical estimate of death is anything but a provisional statement- at least before more obvious signs, like decay, become apparent. People diagnosed as brain- dead sometimes recover after being kept in suspended animation on life- support for years. It's surprising, and a challenge to diagnostic procedures, but not to philosophy.

No, if they recover, whatever a diagnosis said, they weren't dead. Doctors can be wrong, you know.

Incidentally, it's why in my old age I tend to prefer funerals to weddings- the protagonist doesn't come back a couple of years later, saying it was all a mistake, they've changed their mind...