If a husband takes his wife's last name, should I leave his name as his birthname or add his wife's last name behind his?
Use birth names in genealogy. This applies regardless of sex or gender.
However, it's an unusual enough situation that you should add his married name under Other Information.
Thank you. I put his married name under alternate name labeled married name. I left his birth name as his name on his detailed page. I can change if needed, but I believe your answer agrees with what I did. Thank you again.