@ChristinaLopez,
Hi, my name is Christina and I'm a tour guide and student at Columbia GS. My path to GS is similar to yours in many ways and I want to encourage you to apply!
To address your biggest question, you would be required to submit your high school transcripts and SAT scores, however, your college GPA is excellent, and that goes a long way. Although you may not have done as well as you'd have liked in high school (or on your SATs), the fact that you excelled in college shows that you have grown, and that you have the capacity and drive to excel academically. Your inclusion on the Dean's List and your membership in Phi Theta Kappa further support this.
As you are probably aware, GS is specifically designed for students who've had at least a one-year break in their education, as you have. Your reason for taking a break is understandable and admirable, and it shows maturity. As for the fact that you did not volunteer or participate in extra-curricular activities, I think your reasons for not doing so are very strong. I also did not volunteer or participate in extra-curricular activities, so this is definitely not a deal-breaker. These are all things you would want to address in your admissions essay.
Bottom line, many students at GS have less than "perfect" records, for many different reasons. The GS admissions team is not looking for a specific test score or grade. They are looking at the entire person, and what they are looking for is students who have both the desire and ability to succeed at Columbia.
You have until June 1 to apply. Check out the website (I can't post the address as a new member, but a quick Google search should suffice) for more information, and please let me know if you have any other questions!
Christina Gray