Yes, the premise under discussion is that God knows that Schraf will not believe. If you reject the idea that God has that sort of foreknowledge then your view is rather at odds with the idea being defended here.
As to Biblical support I suggest you consider the well-known prediction that Peter would deny Jesus 3 times before the cock crowed. If true that reveals fairly detailed prior knowledge of human decisions (not only Peter, but the people he encounters).
But y you probably ought to be discussing your ideas on the thread about how propecy works.