Before you do anything, make back ups of your back ups. The Level Editor automatically makes them, and one of them may still be good. If you mess around too much they might be written over.
Can you not test your level from the editor, or can you not open it with the editor? If it's the second option, then I doubt it's your World.ini. The original editor doesn't use it.
I had luck opening a corrupted file with Xoft's Level Composer (http://nifflas.lpchip.nl/index.php?topic=165). But, your situation sounds different.
Edit: I'm willing to take a look at it for you.