At least you're being consistent in your denial of anthropomorphisms. Are you denying Gods exhaustive knowledge of the
present and past, also? Most open theists would have a problem with that. A literal interpretation of
Gen 18 leads to the conclusion that God knows neither the past sins of Sodom, nor the present state of the city. The literal reading of this text as attributing ignorance to God is not only, imo, a failure in exegesis (failing to take a figure of speech as a figure) - but
also fundamentally abhorrent to Christian theism.
First, God had promised
unconditionally more than once that He would make of Abraham a great nation. So any suggestion that God may possibly have to find someone else is, dare I say, impossible.
Second, God knew exactly what was in Abraham's heart as he trekked up the mountain, and Abraham even expressed his faith that he and Isaac would return (Gen, 22:5). It didn't take the raising of the knife for God to know Abraham's God fearing heart. He clearly already knew this about him.
And third, what did the 'openness god' learn from this test? Simply this, that in this one instance, Abraham fears God. Now this god can compile the data and make astute predictions about the probablity of the future faithfulness on Abraham's part. However, the openess god has no guarantee that Abraham will be faithful in the future. What assurances could God have to say Abraham would remain faithful in the future? This turns the "now I know" statement into nothing more than a mere transient comment/feeling.