x1tms357mhit The launcher crashing when you click one of the tabs is a Known Issue on Macs with the newest OS installed:
Launcher crashes when I open the downloads tab in Sims 3 | EA Forums - 12167613
So it may have nothing to do with your main issue. For that, please move the Sims 3 folder out of Documents > Electronic Arts and onto your desktop, but don't delete it since you won't be able to reinstall any content through the launcher. Just see whether you can start a new save with the folder removed.
If the Sims 3 folder copies instead of moving, or you get an error when trying to move it, let me know.