I think you're choosing a decent list of schools - Columbia would be a big stretch if you're applying for Regular Decision (since they only have two rounds - Early Decision and Regular Decision).
The other schools are sweet spots to stretches depending on how well you execute the applications. If you want safeties,look at schools outside the top 16 such as USC, UNC, Georgetown, Emory, etc. If I were you I'd swap out Columbia for one of these schools, and you should be able to get into at least one of the schools.
As for the essays, it's not about formal leadership per se, but leadership *potential* - most people applying to full-time programs don't have formal leadership experience (they're too young or inexperienced - most have 3 - 6 years post college work experience and are therefore mostly junior level employees). So it's all about showing the traits that are necessary for effective leadership - decisiveness, ability to nurture relationships with people, communication skills, and so forth (i.e. the sorts of traits that you think make a great boss to work for).
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