Hi
It probably is a cider issue, many of the problems on Mac are. However there are few things you can try.
You mention that you've installed the game a few times. Make sure you do a clean uninstall before reinstalling. When you uninstall TS3 games on your Mac using the uninstaller, the game leaves behind stray files and isn't completely removed from your computer. These files may conflict with future installations. It is best to completely remove them. BluebellFlora's website provides a guide on how to do this:
http://bluebellflora.com/the-sims-3-on-a-mac/how-to-do-a-clean-uninstall-and-reinstall-on-a-mac/
After cleanly uninstalling, install the base game and patch it up to date. If you cannot update via the Launcher, download and apply the latest cumulative manual patch (called the superpatch) for Mac.
Next, be sure to purge your RAM while you are playing. This helps Mac simmers to get around the fact that the game chews through memory like you wouldn't believe. See BluebellFlora's guide on how to do this: http://bluebellflora.com/the-sims-3-on-a-mac/resetting-ram-during-gameplay/
I restart my computer before I play TS3. The memory used as seen in Activity Monitor is at about 3GB after the restart. If I open the Launcher it goes up to around 11 GB (that's all I've done - just opened the Launcher!). At this point I reset the RAM. Then I hit play and get through the opening sequence. I then press cmd-return to put the game in windowed mode from time to time while playing (and always before saving or using CAS). That way I can keep an eye on the memory and reset RAM if necessary. Being in windowed mode also allows you to close the game using force quit if it freezes up - it's better to crash the game than your whole computer.
Another tip is to save frequently. I save at least once per sim day. Use the option to 'Save' or 'Save As', rather than the combined 'Save and Quit'.
Try lowering your graphics settings if you haven't already.
If you are using any mods or CC, make sure they match your patch level. Remove them if you are not sure.
Good luck!
Caspin
