What's an example of a tough CS question? Maybe you're getting shot down because the interviews you've been getting are unreasonable, or maybe you're getting shot down because there's a real deficit, at which point you'd need to make a decision between a career in software or something else. Both are equally plausible scenarios.
There's nothing intrinsically meaningful about your CS grades, so let's not interrogate those.
You're too young to have anything "completely destroyed" by a GPA and a couple bad interviews.
Well I was asked to parallelize a loop where it was totally unobvious in one interview something like a sum of elements in an array where elements are replaced by the sum of elements from the previous elements(they didnt even shake my hand they just showed me the door silently), in another I had 30 minutes to design an algo that outputs from a matrix it's spiral in C(I think I know how to do this now but I couldn't solve it and program it there under pressure in 30 minutes and my solution is ugly), in another I had to use a semaphore to make a loop that increments up to some number and I didn't know what a semaphore was, I had to find if a linked list was looping, I had to write a code that deletes duplicate elements from a linked list and puts them in to a new sorted list in 30 minutes, the financial engineering jobs required the transcript so they didn't work out. I think I like CS and blame a lack of attention or preparedness for the grades. Maybe I am deluding myself though and need to move on.
You need more practice coding, because it doesn't look like you got a strong intuitive grasp for it from school. Those aren't great interview questions, but they're not serious CS problems either.
Also, you should definitely know what a semaphore is. Write some threaded Python code to get a feel for concurrency.
There's nothing intrinsically meaningful about your CS grades, so let's not interrogate those.
You're too young to have anything "completely destroyed" by a GPA and a couple bad interviews.