I did it! After 9 hours of trying to solve the problem, I’m leaving the solution here for those as unlucky as I was. In the case mentioned above, where any direct or indirect interaction with the file caused freezing, it’s something extremely critical, because even running installations of other apps would still freeze the computer. But luckily, before the problem reached that level, I had created a system image (a restore point) from when I had deleted and installed FxSound several times before digging deeper into the problem itself. If you’re facing this critical issue and don’t have a restore point, I’m sorry to say that my solution might not work for you, because this has become an issue with your computer as well, not just FxSound.
When I restored to the previous point, I installed FxSound and checked if it would freeze the computer (which it did again). After that, I uninstalled and reinstalled it and checked if my computer recognized FxSound (it didn’t). Then, I went to the Device Manager and checked if the FxSound driver was there (it wasn’t, even showing hidden devices), so I manually installed the driver. After finishing, I checked Device Manager again, and there it was! Right after, I restarted the computer, and when it booted, I launched the app, and it worked perfectly. Then I set it to start with the computer and restarted again to see if anything would happen, and luckily, nothing bad occurred.
Note: FxSound may freeze the computer if the “startup applications” option is checked, making it impossible to do anything. To fix this, just boot the computer into safe mode and disable that option there.
Note 2: I couldn’t provide detailed instructions or sources for the posts I used because I’m tired and very sleepy, but everything I mentioned is relatively simple to do, and most of the detailed information is here:
1-Oops thread: Oops there's an issue with your playback device settings [OOPS ERROR]
2-How to manually install FxSound’s driver:
Note 3: I still don’t know the exact cause of the error, but it happened when I tried to update Spicetify, and it failed. I don’t know how, but this somehow caused the FxSound issue.