Don't be down, there are tons of people that have been dinged already from Columbia and elsewhere. The fact of the matter is that they saw something they liked in you, and that in and of itself is a testament to you. Take pride in knowing that a Top 10 business school thinks highly enough of you to dedicate a lot of their time to take another look. Trust me, it hurts the first few days but I came away from my UChicago ding more motivated than ever.
In terms of your R2 plans, the first question I would ask is whether you would actually want to attend those two programs. If not, then I wouldn't waste your time unless you felt like the extra essay writing could be useful practice. If that was the case, I'd find a school that offers feedback for candidates and in the event that you got dinged (which could happen if you don't put your heart and soul into it) they could lay out potential weaknesses in your app that you could then address when applying next year to Columbia.
I will say this, you're a strong candidate and it would be a shame if you simply put all of your eggs into the Columbia basket. There are terrific schools all over this country and I think you'd make a lasting impact at many of them, and many of them would make a lasting impact on you.
Pick yourself up, dust yourself off and take a few days to regroup (go enjoy some hobbies or something to get your mind off of it). If after these two or three days you feel you want to give R2 a go get back on this board, ask some questions to find out which schools you'd want to apply to and pour your heart and soul into those apps over the next month.
Good luck to you.