1) Certain things inescapably are brought about by the will of God; i.e., they are predestined. The Incarnation was one of those, since I believe God always intended that he would walk among us and share our lives; the Crucifixion was a response to sin, so that Christ would identify with us in our deaths so that we could identify with him in his Resurrection. This is Christus Victor theology, and is nothing new. If God predestines it, then he knows it will happen, even if it takes some unexpected shapes.
2) Even if God does not know exactly what shape the future will take, he knows how to read the signs. I felt the air getting cold today, and saw clouds gathering and said, "It's going to rain." If I had told Rachel about it, she doubtless could have impressed her friends with her prognosticatory abilities.
Thus God can see trouble brewing in the empires, hatred stewing for Paul, and know with certainty "Thus-and-such will happen." If God knows all that can be known, he can still hazard a pretty good guess about things are going to work out in the forseeable future, right? Many of them would fall under "absolute certainty."
3) I'm not describing the Almighty as a clockmaker who created the world and is letting it run down on its own. He is an Author who remains inextricably involved with his story, and who is capable of nudging things in whatever direction he chooses to send them.
He is a Musician leading a free-form jam session, guided by the rules and structure that separate music from mere noise, yet still capable of guiding the band through crescendos and decrescendos, across movements and toward a final fermata where he wants it.
He is a Choreographer, set upon the stage with his troupe in an improvisational dance; yet though he dances among them, they follow his lead through moves we have no name for. History remains his to guide and direct, and he can do that through a miracle that sounds as a trumpet blast that tears the caps off mountains, or through the quiet voice that whispers in our hearts.
If he wants something to happen, he can make it do so.
4) Many prophecies concerning Christ were not solely concerned with him. The prophecy "The almah [maiden, virgin] shall be with child," for instance, referred to the events in the reign of Ahaz; later, the gospels writers saw something in that that spoke to them of Christ, and they included it. That we associate it primarily with the birth of Jesus and not with the promise of deliverance from the Assyrians that Isaiah made, is due to the emphasis our liturgical calendar places on that verse in light of its citation as a messianic prophecy.
Psalm 22 unquestionably resonates with the experience of Christ on the Cross, but so do virtually all the psalms about how the psalmist feels abandoned by God.
I don't know what David was thinking when he wrote that psalm -- it could easily have been written about his experience fleeing from Absalom after the prince had wrested the kingdom from him -- but my point remains the same: David's suffering and anguish over being defenseless before his enemies resonates with Christ's suffering and anguish on the Cross, much in the same way that we can identify with his suffering when the chips are rock-bottom down for us.