wingchun100
Senior Master
You need to get clarification on the recent comment and I suggest that you consider working through it with him part of your training.
In answer to your question, though. I personally call myself "Sifu" and don't like it when people do refer to themselves that way. Students call their teachers sifu in TMA. I didn't even tell my students to, they just figured it out in time. Point being, that if you were teaching people, they could choose to call you sifu and no one would ha e anything to say about it.
There is not license required to teach martial arts in the US. Literally anyone who someone is willing to learn from is free to do it. What you can't/should do is claim either lineage if they have not expressly granted that privilage. Depending on the lineage, that could get you a visit.
If I may ask, why is it important to you to teach?
Wing Chun has had a tremendous impact on my life. Very early on, it dawned on me that I wanted to help spread the word about it. Also, I get incredible joy from teaching. There were several occasions at the first school where the teacher would introduce me to a new student and ask me to work with them while he tended to other students. He would tell me to help them out with whatever part of the form or whatever technique they were struggling with. I would give them tips on how to improve.
Sometimes, but not always, what I said would cause a revelation. I could see the lightbulb turn on, could see a spark in their eyes as something CLICKED. I can't explain why that is so thrilling to me, but it is.