kaizen1999:
Thanks for reaching out to our community.
Overall, you have a great profile. Some of your extracurricular activities should really be categorized as "hobbies." The difference between an EC and a pastime in this process is that the former is more focused on achievements/results while the latter is something you do purely for fun. There can be overlap, of course, but MiM/graduate schools value folks who demonstrate leadership and an ability to improve their community.
As for the GMAT, since you are starting with a 620, I would try to get as close to 700 as possible. MiM programs are not nearly as competitive as MBA programs, but they still expect around the same scores. What is achievable for you? Do you feel that putting in the time to study for the GMAT could get you anywhere between 50 to 80 points? That would make a big difference.
Lastly, have you considered the GRE instead? That exam might be better for you as an alternative.