@Avareee That is quite the interesting development. I don't know whether the cause of the issue is something involved in Origin's opening of Sims 3, or whether the fully patched game uses some resource that an original disc install does not, but either way, it would narrow things down.
Unfortunately, I don't currently have a disc install myself to compare against and Origin one; like you, most of my packs were purchased digitally. I can make some suggestions for the Origin side of things though. First, disable the Origin in-game overlay: hover over your username, select Application Settings, then the Origin in-game header, and disable the option at the top. Disable all notifications (under the Notifications header) as well. It shouldn't be necessary, but you can also disable Origin in-game at the Sims 3 level by right-clicking on the game tile and selecting Game Properties.
If that doesn't help, try disabling the Origin Client and Web Helper Services. Hit Windows key-R, enter "msconfig" without quotes, click the Startup tab, and uncheck the box next to each one. For good measure, look for an EA Background Service entry and disable that as well. I don't know whether that only gets installed with the EA Desktop App or whether it comes with Origin too, but after I installed the app last year, I caught this service running in the background with Origin a couple times, and it doesn't need to be there.
Finally, try running the game while your computer is offline. You can sign into Origin and put it in offline mode, then disable wifi and/or unplug the ethernet cable before pressing play.
By the way, when you installed via disc, did you let the game patch or run the Super Patch yourself, or did you just play it as-is? I'm curious whether you ran a fully patched disc install at any point—the game changed a lot between its original release and patch 1.67.
As for Restoro, Malwarebytes wasn't saying it was running, just that its files were present, and you could have installed it but never opened it yourself. I do see links to it on sites offering single file downloads, e.g. if you're missing this .dll let this tool install it for you. But it doesn't really matter how you got it, just that it gets removed one way or another.