Thanks for posting, and for sharing a lot of detail into your past experiences. That helps greatly to explain questions that may arise if someone simply glanced at your resume (such as, why the short job durations? Why did you leave Caterpillar? What are you doing now/next?). So I think that you should be able to minimize/mitigate those types of concerns through your explanations in your essays and interview. You do have other things going for you, such as strong academics, sounds like strong test scores, quant and analytical experience, and a good sense of WHY you need the MBA which can really help. You also have a lot of determination that comes across from what you've posted here.
I think you should find a place at one of the programs you mentioned, unless something goes wrong with the GMAT which I wouldn't expect. NUS might be a bit more challenging, and just keep in mind no matter what you need to make sure your essays are really strong, you have a clear sense of who you are and why you need this degree and where you are going with it, and you show why that school is right for you.
Keep us posted on questions and where things go. Let us know if you'd like to speak more as well, we offer a free 30 minute consult at http://www.mbamission.com/consult.php
. Good luck!
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