You have a right to be treated professionally at work, and it's your supervisor's job to make sure all their employees can perform their duties comfortably and safely.

You who have suffered so much do not want to be with the kind of person who makes "black widow" jokes to deal with an uncomfortable, painful moment. You should be with a person capable of great compassion and understanding.

Reciprocating oral sex is, in general, a very good idea!

I'm of the opinion that it is always a kind and appropriate decision to get in touch with someone who's lost a loved one to remind them that you're thinking of them and have fond memories of the deceased.

If this is something you'd truly like to work on, not out of a sense of guilt but because you would enjoy occasionally reciprocating, there are a wealth of resources out there for the enthusiastic amateur (you are far from the only would-be blow-jobber whose spirit is willing but gag reflex is weak). You have more options than "no blow jobs, ever" and "regular whole-hog sessions to completion that result in vomiting."

As long as you don't think he's just pretending not to mind for your sake, it sounds like he has truly accepted that blow jobs are too difficult and painful for you to perform, and he's still very satisfied with your sex life. Take him at his word.

You, too, will someday die, perhaps under inconvenient circumstances, at a time when you do not particularly wish to, and for causes that you cannot yet predict.