Which again means the symlink is not working. I have no idea why not but it is very odd.
Please open Terminal and copy and paste the following search command then hit Enter/Return:
find / -type f -name "*Slot_*" 2>/dev/null
After a little while it will return the results of the search. Please copy and paste the results in a post here.
The problem isn't the symlink, which looks fine, the problem is the mess of a saves folder you have. Maybe your Mods folder is also a bit of a mess? 🙂
There are two external drives, or partitions, showing in the output, what is EXTERNAL 1? The Terminal screenshot you posted previously showed your external is called EXTERNAL, and I can see that in the output too. I'm going to ignore all output returned with EXTERNAL 1 in the file path.
All save files should end in .save. Files that end in .save.ver[number] are backups of the .save file with the corresponding number, they do not load and are there if you want to roll back to a previous save version. You also have save backup files which have a number after the .save ver extension. These are copies the OS has created because you cannot have multiple files with the same name in the same location. These backups will also not load if you remove the .ver extension. In your output you have one save file that should load:
/Volumes/EXTERNAL/Electronic Arts/The Sims 4/saves/Slot_00000002.save
I have no idea about the Mod save folder you have in the save folder, nor the mod file that ends .cwd and am not interested in trying to resolve it. You need to get your vanilla game working before attempting to try with Mods. That is also not a Mod you will get help with here as it raises the age rating of the game.
In short, rename the Sims 4 folder on the external drive, the one in /Volumes/EXTERNAL/Electronic Arts then launch the game and a new one will be created. Immediately quit at the main menu. Now go back to /Volumes/EXTERNAL/Electronic Arts and there will be a new Sims 4 folder in there. Move over the save I mentioned above from the Sims 4 folder you renamed into the saves folder in the new Sims 4 folder that was created. Launch your game, can you load the save from the main menu?
