1. Many top schools (i.e. Harvard) say deferred admission is considered on a case by case basis. Would my startup succeeding be a strong case for deferral?
Certainly could be, yes. This is stronger than personal reasons for sure.
2. Up until what approximate date would I be able to put in a request for deferral with a decent possibility of it being granted?
This is really tough to say. Best to reach out to them directly once deferral is on the table.
3. What top MBA programs allow you to defer your admission?
Most any program will consider it, but granting it is generally case by case as with HBS.
4. If accepted to an MBA program, what will be my appx. decision deadline on whether or not to attend?
They each give you a deposit deadline which is generally in the Spring (April-June timeframe). After that, if you choose not to attend you forfeit your deposit is all.
5. At what point does your age start making it less likely you'd be admitted to a top MBA program?
HBS and Stanford are notorious for targeting students under 29. Other programs regularly take in students in their early 30's, so it depends on the program.
6. What schools will waive application fees for low-income prospective students?
Most of the top schools have an application fee waiver process which can be found on their website. If you don't see it, you can reach out to schools directly and ask.
7. What schools offer the possibility of full-tuition scholarship/fellowship?
All schools have at least some merit based financial aid which is used as incentive for students to attend.
8. How much will I hurt my chances of being accepted to a top MBA program if I take the next two years off to backpack the world? (My profile is provided below)
Well, if you do this, you certainly shouldn't expect them to defer your admission for it. Taking a two year vacation early in your career would likely not bode well for you from an ambition standpoint, unless of course you are independently wealthy, or just sold your company etc. then go for it.