I wouldn't be too worried about the late invite date. I got an invite in early September and it was for quite a bit later. Based on very limited data available, I don't think TT-Lubbock is as pre-match heavy as UTMB or UTSW; I imagine they have quite a few seats still available. Your GPA is a little low, but I think their average MCAT last year was a 29.
General interview advice
Be prepared to explain why you want to be a physician using specific examples and activities that you are in to justify your reasoning. Be prepared to cover any weaknesses, perceived or actual, in your application. Make sure you know enough specifically about TT-Lubbock that you can have some questions prepared for the very end of your interview. Always, always have questions!
TT-Lubbock-specific advice:
Several other people and I had one interview with two people; perhaps it was training for future interviewers. If you see two people, don't freak out-- just make sure you can succinctly explain who you are and what makes you a good applicant. I don't think my trainee was familiar with my application, and that may be similar for you.
You may also get a student interviewer; make sure to treat that interview just as seriously.
I was asked a few questions like "So I see you took the LSAT a few years ago... are you thinking of applying to law school too?" which threw me off a little bit because I was expecting a gentler interview. Just make sure to keep your narrative straight in your head and you should be able to do about as well as anyone.
Finally, if you have a good reason for wanting to be in West Texas, for the love of all that is holy remember to bring it up in your interviews.