A couple of years ago I tried using a thumb ring. And it worked like a champ - my draw weight appeared to magically reduce, and the release action was much smoother than a finger release. After several months, though, my thumb distal of the joint became numb. And it stayed numb for about six months after I ceased using the thumb ring. . . which brings me to what I should have thought of a couple of years ago.

A thumb ring with an extension that covers the pad of my thumb, plus a slight trough that would function as a stop for the bowstring might allow me to use the thumb ring without trashing my thumb.

Has anyone tried such a device? Does it work as I hope? Even if no one has tried such a modification, can anyone suggest or recommend anyone who can make one for me to try? Or is their a manufacturer of such a device?

Mudd has a thread on a thumb release made of leather that works awesome for him.  Do a search and see if it will work for you.