I don't understand how you haven't been invited to more interviews. You're stats are pretty good. How were your EC's? Also, was your RC score low? I know at all of the TX interviews they mentioned how important the RC and Bio scores were. Just a thought.
I don't think that it's too late at all. Keep your head up and maybe try contacting the TX schools to see what the status of your application is. If you've already interviewed at SA then I would also suggest keeping in contact with your interviewer, as well as Dr. C. Remember, in dental school admissions, as in life, connections are everything so use the ones you've made. Good luck to you man.