I think there is more truth to the Solitary God than you might think. I think it is probably true that there was once a Solitary God that somehow split into the Hundred. Maybe the SG doesn't exist as it once did, but I think it is still around somewhere. More and more I feel like no one knows the real truth in Earwa, but that it lies somewhere in the gray area between the opposing views of the world that we receive from each character.
So, in this case, it isn't that the SG does or does not exist, which is the question we are given in the book, but rather he used too exist and yet somehow still does, which is combination of what the nonmen, inrithi, and fanim have all told us.
But thats just me going mad

. Maybe someone else can provide a more sober answer.