I answered your latter questions in a separate post.
The difference between a 740 to a 750 is not insignificant. I think that is a definite worthwhile endeavor. Especially for an ORM.
As long as it doesn't have any negative effects on developing other things like maybe join Toastmasters or getting a board position.
However I would not plan to tinker around with a GMAT for two years I do think it will be a pain in the butt, and possibly slow down your velocity with getting that very well needed ***leadership and impact in your extracurriculars***.
Just keep in mind that when you're an over represented minority you want to differentiate your profile so that there's less pressure on your GMAT score. If they see you as distinct from the pack then The GMAT is less of a tiebreaker.
Re GMAT. I would make a clear plan to do this in a six-week sprint, go for it and then if you need to do another six week sprint.
I would also think about what are you going to do differently this time to get a different result.
I tell people I don't like the try harder do better GMAT strategy. You need to change the inputs.
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