To answer the first question, likely not. The answer to the second question is I am pretty sure. In my bios, I have secure boot control as disabled and secure boot grayed out on the "Not Active" setting

Sorry for the late answer, I am not receiving notifications for some reason.

The root partition is 507GB long and it shouldn't be anywhere close to full since I'd just installed fedora. And even if it were abnormally small/full, the pen should still have worked, so the issue has likely nothing to do with something like a partition.

Honestly, the fact that the pen stopped booting too, but only in my pc (it works in other pcs) makes this by far the strangest issue I have seen to date, so it could have had an equally strange cause. Is there any specific reason why you asked this question :)? I'd be happy to dig further.

Nope. It is 512MB long and still has half its space left. And even if that were the case, the pen where I burned the fedora live iso would still boot :(