Sorry about the rough road. That 715 is an awesome score - that's a 760 equivalent!
I have known another candidate who was about your age and got into Booth... many years ago.

It is good have applied to a range of programs and received consistent results. not great results but it is a data point you can use. The schools clearly did not think they were a good fit for you or vice versa. Most often for such strong candidates as yourself, this is likely because they did not feel comfortable with your post MBA goals and how they would help. perhaps having a PT job (not having a FT job was misinterpreted). Not sure if you have written a letter about it to clarify - schools like people who work 2 jobs (unless you are rich enough at that point) because that signals to them that a person is going to work double hard and will find employment super easily after graduation.

I am assuming you worked with a consultant? If so, I would get their opinion. If not, I would get one to review your details (for $300-500 ) and give you an idea why. Perhaps have 2 different ones review and give you an idea of what kept you out and what it will take to succeed. Those were the only red flags I could see potentially (and they may have been covered, I just don't know) but to summarize them:
1. Post MBA goal
2. PT employment

In terms of your dilemma - it really dpeends on what you were hoping to get out of the MBA. You have a very strong profile for some of the lower ranked schools so I hope they gave you some $$ but they will be quite barren when it comes to IB recruiting most likely and you will stick out as a sore thumb among the HBS, Booth, and even Darden folks. I would probably make the decision after speaking with a few consultants and getting their feedback. Don't think it is a waste as certainty is worth quite a bit these days and you will have certainty about whether you should take the bird in the hand or pursue a few in the sky.

-BB

"To go now or try again" is a tough and risky trade off. If you decide to try again next year, your age and work experience would have increased further (assuming it was one of the issues for Kellogg, etc.). From IB to IB was a very plausible direction - so I do not think that was a cause of concern to the marquee schools. If you used the relevant sections to convincingly explain the gaps and life situations, then that also could not have been a reason of concern (and both these 'ifs' are big 'ifs'). If none of the schools where you have admission will get you into IB, and that was the goal you presented in the applications, then rethink your motivations to have applied to them in the first place.

To go now or try again - will remain your decision and yours alone.

- Dee (admissions consultant)