Awesome points by rtbs15. I wholeheartedly agree. It sounds a bit like applicant's remorse. Which is totally common so do not feel bad about it. We all have opinions and then we change them as we get feedback (admit, ding, WL, etc). As mentioned, if you are looking for IB jobs, Darden is an awesome choice and hard to beat. Yes, the loan is scarry, but not sure what options you will have.
I would perhaps make one comment - while you did get a WL at Darden, and that's an indicator, I feel it still should be possible to improve your profile by working on the essays, applying your Darden application experience, etc. I would hate to just sit a twiddle my thumbs and just be burning time (again, you have an admit in your back pocket to your dream school).
At the same time, I don't know if you can count on getting into a top 10 with a scholarship but again, you won't know if you don't try. Would you be happy to go to Tepper or McCombs with a 50% scholarship or Jones/Owen with a full scholarship? I am totally hoping you would do much better than that but we only have a single data point and we don't know much about you (not that I am saying I am dying to learn about your life in intricate details
but I am saying as one stranger on the internet to another).
My take on this would be - you have an opportunity now and unless you are really busy, I am concerned you will regret not taking it (I would) so I am thinking you accept Darden and then work on resolving regrets so they don't haunt you on those cold nights when you watch your balance grow.