It appears that you can't see the forest for the trees. The Children of Israel were in dispute over many things, the status of Jesus being only one of them. Some believed he was a heretic, so the Qur'an cleared him of that charge by confirming that he indeed was the Messiah that God sent to them (Children of Israel). Some claimed him to be the Son of God, so the Qur'an cleared him of that charge by confirming that Jesus had no father and, more importantly, that God has no children. Some claimed that he was crucified and died, an act that according to the Bible would have been sufficient proof against his being the Messiah, so the Qur'an confirmed that he was not crucified and did not die. Some claimed that he failed in his mission and therefore was not the Messiah, so the Qur'an and Hadeeth confirmed that he would return to complete his mission. The details of the disagreement that the Children of Israel, and others, have concerning the truth are within the Qur'an, if only they were to consult it for proper guidance.
As for the word 'messiah', it is a title and means 'anointed one'. It is synonymous with the Greek term 'christ'. It refers to a special prophet sent by God specifically to the Children of Israel to basically establish God's law upon the earth. So in reality it doesn't mean what most Christians think it does. The Qur'an confirms that Jesus is indeed the true Messiah, as opposed to the False Messiah that will near the Hour. As for the details of his mission, then you would have to refer to the statements of Prophet Muhammad, as instructed in the Qur'an.