Hi there,
We had already been discussing your profile and experiences on the
Manhattan GMAT board for a while, good to see you here as well.
So the 750 is confirmed, correct? Just clarifying because you mentioned practice tests right afterwards.
If so congrats, that is excellent!
We had discussed that I thought overall you have a strong profile and your nuclear engineering experience will help you stand out, and you've done a good job pre-empting any concerns in what you've written about getting a 3rd masters degree. You've also got strong grades and international experience, plus the start-up experience, going for you.
I would encourage you to go for it with your schools list, realizing of course that HBS is challenging for ANYONE even with a great profile, but your ESSAYS are going to be the last key/critical piece for you! The essays are where schools learn about YOU.... who you are; what makes you unique; what you are passionate about; what you'll bring to the class; why you want the MBA; what you will do with the degree; what type of an alum will you likely be??? Don't underestimate the importance of those essays.
And keep in mind how time-consuming each application is... many applicants find that applying to 3-4 schools is all they have time for. Think about the time you have, whether you'll apply for different rounds, your priorities in terms of schools, and remember you'll need to tailor each application and essays to each school and show you THAT SCHOOL is the best fit for you hands down!
Keep us posted and good luck.