It has been explained on a site that the white sword is the master sword, but the name was forgotten through time and was called the white sword because it shined with light. Same deal with silver arrows....
And you forget the part where Link weakens him in OOT and captures him, then in WW he's back, where he gets killed by the master sword. It get's stuck in his head and he is bueried under the surface. Ganondorf died there, left only Ganon now. This Ganon was again even more weakened and captured. In the first Zelda game (which is the second last in the timeline) Ganon is killed. That was a weaker Ganon, and only Ganon, not Ganondorf/Ganon.....
You fail to explain why it would actually work on him. You seem to think that because it is causing more damage it will work. Like if you shoot a bullet on someone and it doesn't even give them a wound, then the golden gun in the James Bond series will work because it can instantly kill the victim. The thing is that it is the same kind of damage but on a more devestating degree. I don't see why it would work....
And Ganondorf isn't exactly gonna wait and see what happens, he can...
Dodge.
Shield himself with his robe.
Use his own power against it.
Hmm, I've never seen Cloud collapse a building with his mind alone, he still defeated Seprioth....