Is my multi-entry Non-O visa valid after my divorce, and can I re-enter Thailand?

Okay, IF you have a year long, multi-entry Non-O visa based on marriage to a thai that you got from a thai consulate in another country which expires Nov 2021

AND

you had an entry stamp dated 4 March it means you entered the country around the 5 Dec 2020.

Then you applied for a 60 day extension and now your stamp is good until 3 May 2021.

To answer your questions;

1 - No, your VISA can't be cancelled whether you divorce or not it's good until it's "valid until" date stamped on the visa sticker

2 - Yes, even if you get divorced your current entry stamp and any extension on it is still valid (other than a year marriage extension).

And

if you could exit/re-enter the country you would get stamped back in with that visa for another 90 days like a Non-O multi-entry visa works