1) What are my chances overall at many of the top 10 schools? Particularly Columbia? Targeting this school with everything I have got.
I think your chances are good--you have many unique profile attributes which means you will stand out as memorable. Most notably, your non-profit startup is a success story and will blow away other applicants who only have participant experience. Your GMAT puts you solidly in the running for Columbia and other top 10 schools, so I would not worry about getting any better on the GMAT.
2) Would attaining a certification in one of their Engineering programs (Columbia) assist me in gaining admission? What about a short 10-month masters in Energy Management/Energy Engineering (MS, Energy Management) from Texas A&M, via their distance program?
You have more than enough education and certificates to qualify you for admission--any more may risk looking like you are trying too hard to get credentials at the expense of your career instead of in support of your career.
3) What can I do as a 26 year old to help me in the next 2 years to gain admission? My undergraduate GPA is really hurting me, but I didn't really know better as a youthful and naive 17/18 year old. I didn't show too much steady improvement over the years because Oil and Gas engineering internships fell to personable students as myself, when oil was booming.
Your GPA rounds up to a 3, which is respectable in the field of engineering. Granted you did not go to a top 10 undergrad college, but your GMAT makes up for it. I would actually try to apply now--you are in the sweet spot and don't see how another two years of work experience will really help you unless you start managing others. My guess is that you could get into a top 10 school with a well crafted R2 application.