Is it permissible for a woman, out of respect and jest, to say to her husband: "My Master" (ya mawlay), or "My Sultan" (ya sultan)?

There is no harm in using the term "mawla" for a husband. The word "mawla" is used for a beloved, a friend, a supporter, and so on, and it is not exclusive to Allah, glory be to Him. A man has authority over his wife and household.