He was single at the time. You definitely have the right mindset. Most people who end up succeeding in their careers, or life for that matter, are persistant and dedicated.
As for the co-worker at Booth, I agree that he will find a job eventually, in the meantime, I hope he is reaching out to his network, applying, and doing his research to land the right position.
My friend was always interested in Rwanda after doing his thesis on the genocide there, so he spent some time with a French NGO developing maternal health programs and delivery. In terms of non-profit work, it does not have to be glamorous and you don’t need to find a cure for cancer either. It looks like you have some good experience already - it would be good to weave that into the essays and eventually interviews.
I work with a lot of MBAs and have friends who have pursued the degree. I am still debating whether its worthwhile for me. I’m in banking so the opportunity costs become significantly higher. Also I am evaluating exit opps into PE, so I might not even need the degree. Again all the best, you’ll do brilliantly as long as you put in the time.