I agree. That's why I think there are places in the Bible where the Bible must be incorrect because God is said to change his mind or be surprised. Either God must not be omniscient or the Bible must be wrong.
There are other choices.
1. Omniscience doesn't mean what you think it does. (The open theist's answer)
2. God changing his mind or being surprised doesn't mean what you think it does. (anthropopathic answer)
3. God being the creator of time means that a thing can be changed that "had been" but "suddenly is" or "suddenly never was." (the "God outside time" answer)
You're right to make the choice for God's omniscience. But maybe you can look at the Bible as instructional as well as historical so that we're not slandering God's word as "incorrect.".
IMO, God does not "change His mind." Every word of Scripture is one, complete retelling of God's plan for His creation and how He has accomplished the salvation of His people. (By the grace of God, all Trinitarian Christians who possess a true faith in Jesus Christ are among the elect, chosen by God from all nations and races and times.)
But just like God became man in order to reach our human minds and become a human substitution as payment for our sins, God likewise instructs His people with human words and vocabulary, using Scripture in the if/then conditional subjunctive tense -- "if you do this; then that will happen."
But none of this supersedes God's righteous and complete sovereignty. Every leaf falls by the hand of God. Every hair numbered.
The greatest paradox for the Christian mind to grasp is the Trinity. Once we get that one, concepts like Predestination and eternity should be easy.