With the spring off, does it close smoothly by hand? Meaning that in that last area that won't close without the spring snapping it doesn't exibit a bind when closing by hand.

If it operates smoothly, you might want to try a stronger spring. You might be able to remove a loop or so from the spring and bend a new tang. The thing is that it's tempered steel, so cutting/rebending may create a weak spot where it's bent. I've seen it go both ways with what appear to be similar springs: One can be cut/bent without problems, another one will break when you bend a new tang, and yet another will fail sometime after cutting/bending.