Sorry it's late and your post is long (English is not my mother tongue), so I'm not sure if I understand everything you are saying. I'll try to explain what happens, if you install something through the Launcher, maybe your question is answered, if not, please ask again.
Sims3packs are actually just a container for either sims or package files. When you install one through the launcher, it gets unpacked and the contained files are copied into the DCBackup, Library or the SavedSims folder. Everything that goes into the DCBackup Folder is also installed into the DCCache folder into those *.dbc (3rd Party cc) or the *.ebc files (Store stuff). The DCBackup is what it says, just a backup. It has no influence whatsoever whether the stuff shows up in the game or the launcher. It's all in the DCCache folder. This is only true for cloth, shoes, hair, patterns, etc.
Sims, Houses, Households and worlds are different. I don't really know how worlds work though. They are somehow in the DCCache and the WorldChaches folder. Not sure if Sims, houses and households also are in the DCCache files but I don't think so. Those can be removed by removing the files from the Library and SavedSims folder.
To get rid of everything else, you simply move the files in DCCache and all should be gone from the Launcher.
Now there are these few pesky files that come with sims and are actually package files. Skins come like that and some other stuff. You can only delete those, if you delete the corresponding sim it came with. There seems also that the launcher does not show all stuff but that should be removed anyway when you delete the DCCache files.
So to get rid of everything from you game you would need to empty the following folders:
- DCCache, Library, SavedSims, Mods & WorldCache
It's also never bad to delete the cache files.
Does that explain what you wanted to know ?
If not, I'll try again tomorrow.
