@kwohld Okay, try restoring the old folder and removing the relevant files. Inside the Sims 3 folder, move the Downloads folder elsewhere. (This contains downloaded Sims3Packs, which don't get deleted when you install the content.) Remove the entire DCBackup folder. Go into DCCache and remove all the files that end in .ebc or .tmp. Go into InstalledWorlds and remove the .world files for any Store worlds.
This should remove all your Store content from the game without touching anything else. Please try again to download a Store item and let me know whether it works.
If you're still asked to sign in, try clearing Edge's Internet Explorer data, which is where the launcher stores some user information.
https://support.microsoft.com/en-us/microsoft-edge/view-and-delete-browser-history-in-microsoft-edge-00cf7943-a9e1-975a-a33d-ac10ce454ca4