Yes, everything's working as intended now.
I couldn't install Movie Stuff because... it was already installed, which I thought might be the case since items from the pack were in my fresh install. I'm thinking that the install process must have tried installing it again after it had already installed, but I'm not sure why.
The handful of Pets-linked items from the Store, and the DJ booth that was a free preorder thing (I think) from one of the packs also finally installed. The pack had already been installed, and I own it... so I'm not sure why the installer wasn't recognizing that. At that point though I had almost everything but those few items working, so considered that a minor issue along with the weird failed efforts the app was making to install a pack it had apparently already installed. At least, it must have, because now when I check it shows a "play" button, not anything related to installing--and as I said I'd seen that items from the pack seemed to be in my game.
Thank you for fixing it, I greatly appreciate it. I probably won't be uninstalling Sims 3 for a while now, even though it takes a lot of space, just because I don't want to reinstall it again anytime soon!