There's a huge piece of me that gives assent to what you say. Absolute Foreknowledge assures that God knows everything at the time he sets "the world" into motion. Therefore, He begins the world knowing who will and who will not be ultimately saved.
However, then there's P-Marlowe's view about God's eternal nature; that is, God can equally inhabit the past, present, and future. And thus, P'M's comment: BTW I believe that you can pray that prayer (of salvation) now and God can STILL predestine him from the foundation of the earth.
In other words, new things can happen in the present and future because God also inhabits the past. He is "from everlasting to everlasting."
P-M makes an awesome point.
New to us, certainly.
Nothing is "new" to God.
You seem to struggle with the idea of prayer and the hope that prayer can actually change problems, life, God's attitude. A pastor probably spends a lot of time nudging people to bring their problems to God so that their prayers can be answered.
But God knows our problems; He arranged for them. He knows our prayers before they're offered; He put them on our lips.
And He created you to be the light for your flock to follow towards Him.