You are off to a great start! Provided you do well on your MCAT and you have some success with publishing in the upcoming year, you will be a very strong candidate even at the top programs. In my opinion you will not need a gap year to improve your application. If you want to take a gap year or years for personal reasons then go for it.
I am currently in my second gap year. During the first, I finished a CNS paper and submitted two patent applications from my undergrad research and during the second I continued with an international masters program. I have had the opportunity to travel a lot, learn a language and do really cool research. Taking gap years has helped me refocus and really improve my application.
There are many ways to build a strong application but significant research involvement and being able to discuss your research contributions during your interviews seems to be a requirement. I do not have a strong preference for pursuing a new project somewhere else for a year or developing your current project further. Both routes have benefits. I actually would say that summarizing your experiences into a cohesive motivation for your application and career path is more important than the specific experience.
I think you will also find that many fellow applicants will have inferiority issues. I would also encourage you to take a breath and relax. You have set yourself up to be a really successful candidate but that is only the beginning of a career as a physician scientist. One year now will seem like nothing later.
You can PM me if you have more specific questions. I also went to a state university and had many of the same feelings and worries that you have expressed.
Best of luck!
