Here's my take on your questions:
1) I don't think your experience as a TA will help very much. B-schools are most interested in "real world" experience. It could be valuable in rounding our your profile (think of it sort of like extracurricular experience), but not asa replacement for work experience.
2) MS may help, but work experience is more valuable in adcomms' eyes than any degrees.
3) You definitely don't need a finance background to get into a top school. The majority of people in top progams do NOT have finance backgrounds. Your bigger challenge will be differentiating yourself from all of the other Indian/IT applicants with big scores and big degrees. Work experience and real community involvement will be critical here.
4) See my comment above. Your school experience is fine, but many other applicants in your shoes have the same thing. What makes you different?
Veritas Prep | GMAT Prep | MBA Admissions Consulting | Co-author, Your MBA Game Plan
Save $100 on Veritas Prep GMAT Courses And Admissions Consulting
For a limited time, receive access to five Veritas Prep Computer Adaptive practice tests when you purchase a Veritas Prep GMAT book! Buy Now!
Enroll now. Pay later. Take advantage of Veritas Prep's flexible payment plan options.
Veritas Prep Reviews