God certainly could have known that Abraham feared Him, for the reasons you gave. It seems that in some cases, God has chosen to limit His knowledge for the sake of relationship with His people.Are we to believe that while Abraham hastened to obey the awful requirement of God, splitting the wood for the sacrifice and journeying three days to the place God would show him, that God did not yet know Abraham feared Him until he raised the knife over Isaac?
This does not negate the fact that there is nothing to know concerning the future choices of free will agents and therefore such choices are unknowable before they are made. Nothwithstanding, there are plenty of knowable facts about those agents which give a sound basis for the possibility of prediction of their choices which may, in fact, turn out to be the ones they will make.
That is an interesting illustration, Homer, of an attempt to reconcile the Scriptures which indicate a lack of knowledge on God's part, with the inconsistent view that God knows in advance every choice that man will make. Although I do not think it is the correct explanation, I acknowledge it's ingenuity.A chemical professor might say to his class "now I will apply an acid to this substance and see what the result will be", knowing full well exactly what will happen. He is speaking from the point of view of the students. Likewise, many things in the bible are written with our viewpoint in mind.