If God's will is that all be saved, and man has free will, and not all men are saved, then God's plan is not accomplished with man having free will. God's ways are not our ways. I also note that you are putting your money on His omniscience INSTEAD of His omnipotence. This of course erases the concept of God even having a plan. God just watches the events of human history, then snaps His fingers and says: "Yep, that's my plan"! :) This isn't God's plan at all, it is God simply signing off on whatever man decides for himself.
If this is your conundrum, you have the same problem without free will:
If God's will is that all be saved.. and not all men are saved, then God's plan is not accomplished.
Your way out of course is: "Aha! God doesn't will that all men be saved!" changing in your mind "Our Father" to "Some of Our's Father."
But then that's your choice. You do have free will after all.
We agree God is omnipotent and omniscience. Free will stares you in the face each morning when you wake up.
How you build a TULIP from this is a major puzzlement to this court, counselor.
Must I "council" you again on God and time? :-) You are putting God on a timeline again.
Remember, God is infinite. In infinity, there is no difference between "omnipotence" and "omniscience". Such things are immeasurable. There is no 'lesser' or 'greater' or focusing on one aspect over another in God.
Now to rattle your pickle...
Every point on an infinite line is the same point! Think about it.
I think this short lesson on "infinity" can help us to understand how God can allow Man's Free Will and His Sovereignty to co-exist without one overriding the other...
Nicholas of Cusa wrote some interesting stuff on comparing God and infinity to Geometry...
Regards