He knew His destiny and His work and the effect it was supposed to have, which effect it did have and so proves the preordination. I don't believe God intiates events that may or may not work. Precise human agency would have to be forseen. 
God never prevented man's volition in the matter. Note Christ's lament when he rode into Jerusalem on the donkey and His people received Him not. The opportunity for the Jews to receive the Messaih did indeed exist. Continued suffering wasn't necessary at that point had the Jews received Him. A decision point was reached and the decision made by the Jews was a rejection of the Messiah.
Again on the cross, Jesus remained obedient to the Father, but I must admit I'm not certain that Jesus Christ knew if he was going to suffer the first death and at that point. One significant point was Jesus Christ's perfect obedience to the Father and His resultant Perfect Sacrifice. An adversary might argue that foreknowledge of this and lack of a decision point on Christ's behalf would eliminate any element of sacrifice.
He knew His destiny and His work and the effect it was supposed to have, which effect it did have and so proves the preordination. I don't believe God intiates events that may or may not work. Precise human agency would have to be forseen.