> That's because my worry is corruption of the entire Library, which Photos stores as one gigantic opaque file/directory abomination. My .photoslibrary file is currently 70gb in size, and I'm terrified of what would happen if it becomes corrupted.
It's a folder that acts like a file.
Right click > Show Package Contents works, and there's an "originals" folder that should have all your photos in normal everyday files.