Apologies for my delay in response. I was out of the country for the past week.
Sounds like you'll certainly be a competitive applicant when you do apply -- great background and stories to use. Age shouldn't be a major factor. In general miliatary guys are older than the median age. I would recommend exploring other career ideas in the mean time before you apply other than IB and consulting. I'd say 80% of military applicants discuss doing one or the other in their essays. It's not bad to end up there, but it's certainly not a position of differentiation. If you do end up there for your essays, I'd definitely spend a lot of time learning about these career tracks and why they're a good fit for you and what you hope to accomplish in pursuing them.
Your GPA is well served by the fact that you ended strong, did well in your Masters and that you pulled a strong GMAT. I wouldn't worry about trying to juice it more.
You should be able to get a lot of mileage out of tutoring immigrants and flying to visit sick kids. Volunteering is always good for the soul, so if there are other opportunities in which you have interest, I'd say go for it. But, I wouldn't do it just to check a box. Your interest in existentialist literature might be a good point of discussion -- ale not so much
.
Depending on whether you lean toward banking or consulting, you might want to look at Tuck and Darden for consulting and Cornell for banking. Michigan is also very strong.
BTW, thanks for your service!