@FreeToBeMae The fact that DISM and sfc can't run to completion indicates a serious system issue of some sort. If you want to try an intermediate step, a repair install would only take a few minutes. Here's how to run one:
https://www.tenforums.com/tutorials/16397-repair-install-windows-10-place-upgrade.html
This shouldn't delete any data, but if you get to step 13 and are NOT asked to keep your personal files and apps, back out and start over. I can't promise that this will help, it may not, but like I said, it's quick and should be painless.
I understand that only Sims 3 has this issue, but that can happen—different games use different resources and can interact with the OS in distinct ways. So it's possible that only Sims 3 is trying to use whatever is damaged on your system. I would guess the timing of the switch to the EA App is a coincidence, but it's also possible that the App is trying to access a damaged or unavailable resource, particularly if Sims 3 is the only EA game you play. I doubt it's an account issue though—in those cases, the App doesn't even let the Sims 3 launcher open.
If you want to test whether the EA App might be at fault, you can try putting it in offline mode, then taking your computer entirely offline, before you play. Disable the background service under Settings > Application as well. To be clear, this will only help if the App itself is the problem, and if it works, it doesn't mean that your computer is fine. But it might be a useful workaround for the time being.