Now you are defining what it means to be a Christian? By whose standard have you decided I am not a Christian? The cross does not symbolize the Trinity, it is a symbol of the Lord's sacrifice.
You are not going to prove that Jesus is not God by using the Qur'an. If you have studied the Bible with any understanding you would know that there is but one God the Father and that Jesus is His Anointed One (Messiah = Christ). You would also understand that Muhammad was not a true prophet of God since Muhammad violated God's commandments and taught others to do the same. He may have tried to use the pen to spread Islam but he used the sword more often than words. We see this tactic today. Muslims in many parts of the world are killing all unbelievers where they find them and killing other Muslims for political reasons.