[The Saucepan Man]

Whereas before, without the Ring, he could be slain and come back, and slain again and come back again.

Why would Sauron create and bind himself to something that had the potential to be utterly destroyed if he himself did not?

My understanding is that, when the Ring was destroyed, Sauron's spirit was cast into the void. Such a fate could equally have befallen him had he not created the Ring. After all, it happened to his Master. From his perspective, the creation of the Ring actually lessened the chances of this occuring, for he was less likely to be overcome.

the possibility that his enemies would resist the corrupting influence of the Ring and actually seek to destroy it was beyond his comprehension.

I am not so sure that it was. He may not have expected two Hobbits to bring it into his backyard with the intention of destroying it, but he knew that no one could destroy it voluntarily. But for the hand of providence, the Ring would have been Sauron's shortly after Frodo claimed it as his own.