Hi,
The game does crash a lot on Macs if you are not updated past a certain point and the issue gets worse when you add more expansions, which is why it probably seemed better when you had only the base game.
As far as I can tell you have three main issues:
1. The game might be installed oddly now because you have done a few uninstall/reinstalls. This means it is best to do a clean uninstall using the directions below and then start from scratch. It takes some time but it'll be worth it if your game then works well.
2. The game isn't updating properly. You can resolve this by downloading and applying the latest manual patch. See patching instructions below.
3. Finally, your game is crashing because it wasn't made properly for the Mac operating system. There are some things you can do to get it working better. See tips for Mac simmers at the bottom.
Let me know if you need more help. Good luck!
Caspin
1. Clean uninstall/reinstall instructions
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.
Check that your game works properly. Then install any EPs and SPs that you own, in order of release date.
2. Manual superpatch
Many simmers find that patching their game via the Game Updates tab of the Launcher does not work properly. It is then better to download and apply the manual superpatch. It is important to download the Mac version rather than the PC version, and to pick the right one for your region.
Instructions and the links to the downloads can be found in the Mac section of the forums at thesims3.com here:
http://forum.thesims3.com/jforum/posts/list/549552.page
If you use any mods or custom content, be sure to remove them before patching.
3. Tips for Mac simmers
Unfortunately a lot of TS3 players encounter problems when playing the game on their Mac. These can include crashing and freezing. A lot of these issues can be avoided or at least improved by the following measures.
Firstly, manually reset your RAM while playing. 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.
Second 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.
Make sure you are patched up to date. The 1.63 patch included fixes for Mac simmers that did actually improve the stability of the game on our operating systems, so it is well worth updating to at least that level. The current patch is 1.67.
For general advice, information and tips on how to play TS3 on a Mac, read BluebellFlora's guide here: http://bluebellflora.com/how-to-play-the-sims-3-on-a-mac/
