Okay, take a deep breath. You might not like this answer, but the second support agent was correct.
Origin provides a means to switch an already installed game from one drive to another. I have no idea how well or poorly it works and which games it will make a mess of (such as TS3 with its EPs as you encountered). May as well stop here. There are no shortcuts that I recognize to fix this properly.
-- Uninstall both games entirely from both drives.
-- Clean the Windows Registry using a product such as
Piriform's CCleaner (the free version is fine).
-- Create a folder yourself on D or whatever the letter drive mapping is of your new, larger SSD. Call the new folder "Program Files on D" or whatever you like.
-- Install your games and EP/SPs onto that new folder; whether these are Origin or disc installs, you should be able to instruct the installer where you want it done (might be called a "custom install" when you get to that step).
As for your user game folders in Documents, those will live on whichever drive your Documents folder is on according to Windows. If you want your Documents folder to really be on D (the game doesn't care as long as it finds your "real" Documents folder), then that needs to be arranged through Windows.
https://www.dummies.com/computers/operating-systems/windows-10/how-to-change-the-location-of-user-folders-in-windows-10
(sorry for the insulting sounding link, but they do have good instructions and illustrations for this)There is a way to keep your Documents folder on C where I assume it is now and use Junction Points to get your user game folders to be on D, but if space is that tight on C there really isn't any reason to pursue that.
And finally, the size of saved games will change as you play them but mod files (you meant the package files in Mods\Packages?) are only read from at startup. They never change unless you are downloading more content and adding to them. Mod settings and options are stored in saved games, not in the Mods files.
