Pre-Existence? Divine Being?

In my latest reading of Christology in the Making: A New Testament Inquiry Into the Origins of the Doctrine of the Incarnation, James D.G. Dunn argues that New Testament passages that are believed to support the pre-existence of Jesus (that Jesus existed in some form prior to his life as a human) actually do nothing of the sort. 
 
Philippians 2:5-11, for Dunn, does not say that Jesus was God and became a man.  Rather, it's contrasting Jesus with Adam: Jesus, unlike Adam in Genesis 3, did not try to attain equality with God but rather humbled himself by embracing death.  When II Corinthians 8:9 says that Jesus was rich yet became poor, Dunn does not think that means that Jesus was rich in a pre-existent state.  Rather, for Dunn, Jesus as a human being enjoyed a rich relationship with God, yet he chose separation from God on the cross.  When I Corinthians 10:4 says that the Israelites from the wilderness drank from the spiritual rock, Christ, Dunn believes that is saying that the rock that brought forth water was a type of Christ, from whom Christians drink.  And, when Colossians 1:15-16 presents Jesus as the firstborn of creation, the creator, and one who was before all things, Dunn argues that Paul was using a wisdom song for a purpose: to show that wisdom finds its fulfillment in Jesus.  For Dunn, Paul in Colossians 1:15-16 does not depict Jesus as pre-existent.

I can't say that I find Dunn's exegesis on some of these passages to be overly convincing.  Regarding Philippians 2:5-11, the hymn appears to emphasize that Jesus had a human likeness or appearance.  That tells me that part of his act of humbling himself was becoming a human being (or appearing as a human being).  I Corinthians 10:4 appears to be saying that the Israelites were somehow partaking of Christ in the wilderness.  And Colossians 1:15-16 seems to present Jesus as pre-existent.  Dunn acknowledges that John and Hebrews lean in that direction.  I think he should say the same thing about Colossians.  But his belief that Paul wrote Colossians may influence his exegesis, for he probably does not want for Paul to uphold Jesus' pre-existence in Colossians, when Dunn has argued that a belief in Jesus' pre-existence is late and came a little while after Paul.

Something else that I found interesting in my latest reading: Dunn discusses what some have considered to be hypostases of God----wisdom, the Memra, the angel of the Lord in parts of the Hebrew Bible, etc.  But Dunn does not think that the Hebrew Bible or Judaism depicts these things as independent divine persons.  Rather, for Dunn, wisdom is a personification, the Memra is a way to convey God's nearness without compromising God's transcendence, and the angel of the Lord is God himself.  This stood out to me because there are elements of Messianic Judaism and Christian apologetics towards Jews that try to argue that there are things like the Trinity in the Hebrew Bible and Judaism----that neither saw God as one person alone but rather was open to a God-like being existing with God.  But Dunn argues the opposite.