Your target list becomes realistic/unrealistic based on your execution.
1. Do not retake the GMAT. A 730 is a great score and your quant is not that low. Contrary to popular opinion a nosebleed GMAT does NOT offset a low GPA. It definitely helps your case, but GPA and GMAT are not interchangeable. Getting a 760+ on the GMAT likely will not get you the ROI you're looking for. The best way to "offset" a low GPA is by creating an alternate transcript. Take 1-2 classes in econ, stats, accounting, etc. at a reputable online school (Harvard Extension, Berkeley Extension, NYU School of Continuing Education, etc) or at a local college. What this does is show schools that you recognize your GPA is a weakness and that you're addressing any concerns it might raise. Plus it's your penance for not doing well in undergrad and show of good faith that you will put forth the effort to do well in grad school. Don't OD on taking classes (no more than three, with 1-2 likely being sufficient). Also write the optional essay. Acknowledge your GPA, take responsibility for it, and then explain any mitigating circumstances. Keep it brief.
2. As you probably already know front office roles go further in bschool applications than back office. However, that is not to say that you can't get into a top program from a support role. I notice that you were placed on very high profile accounts. Use this to your advantage. Have your recommenders speak to the fact that when it comes to projects for their most important clients you're the person they want on the team. That will say a lot about you. The promotion helps your case too. Your resume needs to focus not on your tech skills but on your ability to manage clients, influence people, and achieve quantifiable results.
3. I think the biggest hurdle for you will be to tie your background to your career goals. It's perfectly okay to talk about switching careers (I did it in my essays). However, you need to explicitly tie your background to your desired future. Did you do any IT work for a marketing firm or in a CPG or apparel company's marketing dept? You are going to have to explain why you want to move into marketing/brand management and what applicable skills you have picked up along the way. Look at your ECs as well as WE to find examples of when you did work that's transferable to marketing/brand management.
4. What did you do as the lead coordinator? Did you supervise or manage anyone? Were there opportunities for you to directly lead a team (even on a temporary basis)? Don't simply think of leadership in terms of a title. Leadership is about influence and impact. Can you get people to follow your lead to eventually deliver tangible results? You don't need a title to do that. Tutoring at the charter school and coaching the basketball team can also yield some decent leadership stories for your app.
Overall, a lot will depend on how you execute your application. I do think Kellogg and Columbia would reach schools for your profile, but I don't think it's impossible either. I would add Johnson and Ross to your list of schools to research. Both have slightly higher admit rates and place very well in brand management roles at major companies. They'd be good alternatives to Kellogg if you don't get in.
Hahaha, just read the above exchange between you and Young James. I pretty much just regurgitated his advice. If I added any other insight, then I hope it helps.