How do you get around this problem? Or do you just accept it as a fact?
Let's make certain that you do have my understanding of absolute predestination down correctly.
God not only "knows the future" of this timestream, He has omnitemporally foreknown all possible timestreams (an infinite number), each with different foreknown Ends (i.e., "Sodom repents" vs. "Sodom does not repent"), and God has specifically chosen to create THIS Creation/timestream (in which Sodom did not repent) rather than a differing foreknown Creation/timestream with different Ends (such as one in which Sodom would have repented).
True?? No argument??
If we can agree on that, I'll proceed to the issues of Theodicy.
It would be fixed even if there were no God, or if God did not know it. The future is fixed for the same reason the past is, and it has nothing to do with what anyone knows, not even God.
Consider this. Many believe because the future is fixed, man cannot really be a volitional creature. But no one doubts that the past is fixed, that it is what it will always be and and always was. (How could it ever have been anything else?) We believe God has volition and had it in what is the past to us. But the past is fixed. Therefore, the "fixedness" of the past or future has nothing to do with volition, or what Cavlinists sometimes mean by "free will."
The future is fixed as much for God as it is for us.
Hank