I don't think it is a matter of God's omniscience being "wrong", but that He has already seen what will be - He is outside of time. Scripture says He knows the end from the beginning and, before there was anything, He knew everything that would be. We can't get our minds around that kind of knowledge, nor what it would be like to know all the what if's as well as the what will be's even the what CAN be. Everything He knows will happen WILL happen because He is already there. When people hear God knows what will happen and that all things work together to accomplish His will, they conclude that it means God makes all things happen according to His plan and, by default, toss out our understanding of free will. But, I don't think we should do that.
Think about a game of chess. I used to play it as a teenager and even one time beat my teacher, but I never got to the point of being anywhere near a novice much less an expert at it. Those that are experts, use intelligent "strategy" - they think ahead based on their opponent's moves and responses to their moves. The greatest players could have the game won after the first two moves! They could "see" it all as it unfolded. So, if God already "saw" the whole game from beginning to end, then already knowing how it would end allows Him to work it all out to BE his will. Knowing everything that will happen also means knowing all that MUST happen because it, in truth, already HAS happened. Like I said, it's one of those mysteries that, one day, we will also know - but not with the minds we have now.
I agree that we need to believe we have free will, otherwise, this planet would be a real mess.