My wife's boss Sam is a nervous wreck.
Oh my. Why do you think he's a wreck?
Because his wife keeps telling him what to do and how to do it.
It sounds like he's in a pretty bad marriage.  He needs to learn to stick up for himself a bit more, as people shouldn't let their spouses just run their lives like his wife is.  He might find himself less stressed after learning to be more assertive!
I agree.
I'm glad that you agree. I do hope that you reach out to him and see if you can be of help or try to book an appointment for him and his wife for a couple's counselling.