Apparently, running TS3 without the launcher is a bit of a headache on a Mac. According to our research, the Windows equivalent file on the Mac that bypasses the launcher to run the game is written as a Windows file, which a Mac can't run. The conversion guy must have been on vacation! Anyway, apparently you need to download a free program called Wine which bridges the language barrier between the Windows file and the Mac computer. A reinstall and computer restart should fix things for you, Ricalynn but, should you need this info after all, let me know and I'll get my husband to figure out the specific steps for you.
Good luck with the reinstall.