Friend or partner usually works but there’s other more cute fun things but if your not sure just basic is the way to go and as always. Ask them what they want but in a casual genuine way.
Pet names are very intimate and rarely gendered. I often refer to my partner as poppet - go ahead and guess their gender.
In terms of work acquaintances I think your question is even weirder. Please don’t call your coworkers babe or hunk - names are nice and you should default to using them unless they offer up a nickname and both of you are comfortable with them.
If I’m giving a coworker a nickname, it is usually some riff off of their real name that I know they don’t mind. This should be asked directly after creating it, and not just assumed. Most work friends won’t mind a humorous alternate name that is deployed sparingly and in private.
Maybe but some people may not be comfortable voicing an objection - please be very careful. It’s usually best to only adopt a nickname if it’s offered.
It is definitely case specific. Proceed with caution, always.
What ever you say Munk-o
Not non-binary, but I’m a man of respect and I prefer to be addressed as Padrino.