While I still disagree entirely with your premise (that this universe is caused by the second Pattern) I will admit that in an infinite enough universe (as in Amber) it's possible for there to be a Pattern out there. Though I don't think it's THE Pattern, because that is counter to the cosmology of the Dresden Files as we know it. You can only have one real true origin of everything.
That said, in the interest of fairness, I'd point out that Zelazny did insert himself into the Chronicles of Amber as a minor character. (The guard on the way to the Pattern chamber.)
That said, I disagree with the idea of a truly infinite multiverse that may have Spider-Man or whatnot in it. But that is because it seems to me that new universes are caused by a free will Choice made by a person, and no Choice a person can make is going to alter the rules of reality enough to make a radioactive spider give someone superpowers and not just make them very sick.