@neoromanempire Please repair the game to undo all the changes you made, delete Options.ini from Documents > Electronic Arts > The Sims 3, start a new save, and see how it looks. It's important to establish whether the brightness is due to those changes or to something else on your system.
If the game is still too bright, do you have an HDR monitor, and does it help to disable HDR? Many older games aren't fully compatible with HDR and look bright or washed out or gray, depending on the game in question.
If that isn't relevant either, please run a dxdiag and attach it to your reply.
https://help.ea.com/en-us/help/pc/how-to-gather-dxdiag-information/
