I have a different take on this because I don’t think your grades are necessarily an issue. But the fact that you think they’re the issue… is an issue.
UChicago uses your transcript to figure out if you have the capability to do the work. Beyond that, I don’t think grades get much discussion. They’re not sitting around the table deciding that Applicant X gets in before Applicant Y because Y had two more Bs. Once they’ve determined both X and Y are capable of the work, they’re looking to see which one shows the fit they’re looking for. IMO, if you’re not accepted it won’t be because you had some Bs or didn’t have a 1600.
If your essays and description of the ECs (don’t forget how you describe things is key) shows these are check-the-box type activities vs. a demonstration that you have the curiosity and drive they want… that will be your issue. If you waste any space at all explaining away the Bs, that will be an issue. You need all that space to show how interesting and fascinating your ECs and you as a person are, what you’ve learned, how you’ve grown and will continue to grow.
Much of what you’ve listed appears to be a checklist of things that Tiger Parents want their kids to do, not necessarily things you did because you were curious, interested or fascinated with them (that could be wrong and just a function of the way people tend to list things on this forum, so if that’s not the case, don’t be offended, use that information to know how not to present them on your app.) If your app reads like a checklist of what you thought would make for a good app, that approach tends to fall flat at UChicago. So you need to make sure you communicate why you did these things and how that fits with the UChicago goals and desires. They’re not necessarily looking for the person that checks the most boxes, they want to know why you chose those things, what you learned, what advances you made, how you grew, how you impacted the organization.
Have you done some in-depth research on the UChicago culture, what the college values, what it is trying to achieve? If you’ve done that and you know you are a fit, you are what they’re looking for, this is what you need to show in your app.
One question - your list of colleges is eclectic. Can you give us some insight on how and why you chose these colleges?