There are some practitioners with much less training and certification than you who have become excellent teachers and created lasting martial arts. (Think Helio Gracie and Bruce Lee.) There are other practitioners who have much more training and much higher rank certification than you who couldn't fight their way out of a wet paper bag and teach non-functional garbage. (Not going to name any names here.) I think a big factor will be your personal experience in applying your skills in a live situation: real fights, competitions, hard sparring against tough, skilled opponents. The other major factors will be your teaching skill and your willingness to keep learning and testing your material. As long as you are honest about your experience and qualifications, I don't think you have any ethical problems with teaching.