Hello,
To answer your questions:
1) If you really want to stay on the east coast and you want to work for an elite MC firm, your best bet may be Stern, Columbia, and Yale. I think that Harvard & Wharton may be a bit of a stretch given your GPA, although I wouldn't say they're impossible. That's just a big hole in your story for schools that are that competitive. If you're willing to leave the east coast, Ross, Booth, and Kellogg could also be great options for you.
2) Yes, it's a weakness, but only address it in your optional essay if you have a good story to tell -- e.g., you started off weakly in college but performed better as time went on. Otherwise, don't draw too much attention to it.
3) Any of the top 10-12 schools will get you on-campus interviews with blue chip MC firms... If you're willing to look beyond the east coast, I think you will get in somewhere that can help you land a job with McKinsey.
Good luck!
Scott
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Co-Author, Your MBA Game Plan