The Orthodox Church does not have an administrative center. There is only a taxis of dignity explained by the early councils whereby the Ecumenical Patriarch comes in honor only before his other colleagues if they gather together. This does not mean that he has any authority over them.
God's unity with Christ is a unity of essence because Christ is uncreated in His divine being. He is in the Church, giving Himself to us. We become one with Him by His grace. That is, He makes us one with Him. You are not His partner in essence because your essence is created, but you are with Him by the grace that He sends down upon you.
David's "Be angry and do not sin" means to me that if someone provokes you to the point of anger, don't remain angry. You have nothing against the one who provoked you. Do not sink under the provocation. They want to provoke you so that you will sin. In this case, the Bible says "Be angry and do not sin" in the sense that reacting to harm done to you is reasonable, but reacting against the one who caused it is a sin.
"Christ came to save people but He wants each one of us to follow up on the mission of salvation, to be a savior to those around us. Christ is not only active from heaven: all of us are His hands and His eyes and He has given us the Gospel so that within us and at our hands it will become a glorious reality. In this way, if we love people, then they feel that God loves them. We love so that people may draw near, not only to us but to God. We do not love in order to be loved ourselves. We love so that God may be loved."
Our unity, if we are believers, is God's work through His grace, but along with this it is the work of our desire for the good of all people. God created the world and left it for us to make through our love. The universe does not develope organically from itself. It is human beings who cause it to perish through their sins or make it live through their love.