I’m sorry you are struggling. I hope you have proper medical care now.
The schools you want to transfer into are all reaches. I don’t actually think you are a transfer student. As a medical withdrawal, doesn’t that mean you’re effectively starting from scratch, like a high school senior?
If the high stress environment was too much for you, can I suggest you add some small, more low key schools? I think all you mention here, frankly, might be a bit too much for someone who is clearly fragile and needs to be mindful of mental health. I definitely don’t think Northwestern or USC should remain on your list. They are both really big. Even at Brown, you’re still going to start out with mostly larger, more impersonal classes.
Clearly you are still looking at well regarded colleges, but that doesn’t mean you have to settle for “less.” Look for a low stress environment with collaborative and friendly students. William and Mary, Vanderbilt, Wesleyan, Vassar, Rice, Bates, Middlebury and others are known for being friendly. Brown too, but I’m concerned that the pressure of an Ivy League school might be an issue for you. Look into a few of those I mentioned, and good luck.