Thank you. Those are interesting suggestions that I had not considered before.
主 together with the name of Jesus is "Christ Jesus". I do not know if 主 means the same thing as "Christ" does in Gnosis. I am familiar with this word only in the Christian context and have never heard it used in the Buddhist context. I've heard this word used informally to mean "church" or "christianity". It must have had a meaning before Christian missionaries arrived. Maybe it's a non religious term for "lord" that was borrowed by Christian missionaries looking for a title that didn't have Buddhist connotations. That's a guess only.
主宰 is used to indicate a feudal lord, a landowner. Incidentally it's also used to address lord Voldemort in translations of the Harry Potter series.
I don't speak much Chinese so I could be giving a wrong impression here. I'm commenting on the way these words are used in Vietnamese. But with borrowed Chinese terms like these the meaning is often similar in either language.
The problem is that the english term "master" does not have a direct equivalent that is universal across asian languages. There are many terms that can be used, but all of the terms I know have meanings that do not correspond to "master." Plus, each buddhist tradition has their own terms for levels of attainment, and those terms are not used consistently from group to group.
A term I am interested in as a possible translation but do not know enough about is 主 or 主宰.
"Do not worry; cultivate the habit of being happy." - Samael Aun Weor