first and foremost - welcome to the gmatclub phd (little) community
you sound like a good and promising phd candidate. your story of beoming a research enthusiast is good and not so rare - so there will be no problem in explaining this on the SOP.
your TAship and hopefully some RAship or research oriented work will do miracles to your profile as well.
regarding the GMAT/GRE issue (i did both at various times), the quant section in GRE seem a bit easier than GMAT. the verbal parts in GRE are way more difficult than GMAT, especially for non-native english speakers (like myself) because of the strict vocabulary questions.
it seems that without much effort you can improve your GMAT as well
although - i think going for the GRE is better option (I think retaking the same test after getting a 700 might look a bit odd).
I would also suggest that during the coming months you try to converge to a tentative research focus. some schools look for one in the SOP, and won't do with just "I want to do research in consumer behavior, especially the effects of branding". this doesn't necessarily mean that you'd do exactly that in your PhD, but it is used to assess the match between your interests and the faculty's/ you can read elsewhere in the forum on my opinion on the importanct of such match (very important!).
all in all - your profile seem good and promising and we look forward to hearing how things progress for you (and give some humble advice if you ask nicely...
)