Yes, you can edit options.ini, in Documents > Electronic Arts > The Sims 3, to set your preferred resolution. Crtl-f and search for "resolution" without quotes, and you'll find the value, for example mine says this:
resolution = 1920 1200 0
The zero at the end, or whatever you see, is irrelevant.
By the way, does the game freeze if you switch to windowed mode before changing the resolution? That's another approach, and you can switch back to fullscreen once you've set your resolution to what you want.
If this doesn't help, please make sure you don't have any other applications trying to "optimize" your in-game settings, for example Nvidia's GeForce Experience. This would interfere with your attempts to change any graphics settings and could be causing the freeze.
By the way, the game resets the options.ini file whenever it detects a new graphics driver, so that may explain why your options were reset. However, if your options are now on low, that suggests that your card is being rated improperly. If you're still having trouble with this, please post the first 40 or so lines of deviceconfig.log, also in the Sims 3 folder; stop when you get to Options. You can delete your user and computer names, about 20 lines down; the file doesn't contain any other identifying information.
