@ToBeUnmasked For the launcher error, try clearing the cache for Internet Explorer. Even if you don't use it, the launcher does for some purposes. Be sure to uncheck the box to preserve data for favorites.
clear IE cache: https://kb.wisc.edu/page.php?id=15141
It sounds like you might have a corrupt .dbc file (bundled third-party content in DCCache), bad cc, or some other issue with your TS3 game folder. To test, pull the entire folder out of Documents and onto your desktop. When you launch the game again, a new folder will spawn with no content. Try installing your new cc into this folder. If it works, you've confirmed that the issue is in your old game folder.
It's possible that a clean game folder will take care of the issue, and you'll be able to start installing more cc without having to do anything else. When testing, though, be sure to copy your .dbc files into the new folder rather than just moving them so that you'll have backups if needed. If this works, you can move your saves and other content into the new folder from the old one. (Store content is bundled in .ebc files, also in DCCache, and premium content also requires the ccmerged.package from DCBackup.)
If a clean folder alone doesn't fix the problem, the most thorough way to troubleshoot would be to reinstall all of your sims3packs. It sounds like you have quite a lot of cc, though, so that might take a while. An intermediate step would be to copy all of your .dbc files into the new folder, excluding the most recent one (they're numbered by order of creation, starting with zero). The newest file is the one into which the launcher would be trying and failing to install the new cc. If you confirm that you can install new cc when all the other .dbc files are present in the new folder, you would then only have to rebuild the newest one.
You could also examine your .dbc files for bad cc, looking for any items that you don't remember adding to your game. Uninstalling these items might not fix the issues, but if you don't want to have to track down all of your old cc, it's worth a shot. Crinrict wrote an excellent guide to uninstalling bad cc; scroll down to "Method by Mell":
https://sims3.crinrict.com/en/2011/01/tutorial-how-to-get-rid-of-unwanted-custom-content.html
