The interesting thing that I have discovered through these comments and the comments on my Facebook page is that I have clearly "thought" as an Eastern Orthodox for a long time because the questions I highlight in my blog are the same questions that theologians in the East have asked for centuries. My questions derive specifically from the language that the Church has used in its documents to explain the Immaculate Conception.
The root issue (at least as far as I can pinpoint) on the teaching of the Immaculate Conception is original sin. What appear to be subtle nuances between the Eastern and Western Church are actually two very different perspectives on Original Sin/Ancestral Sin. These two terms do not mean the same thing - and I am by no means capable enough, at this point, of explaining the Orthodox position beyond this simple explanation:
In Catholic teaching, when Adam and Eve sinned against God it damaged our very human nature (Original Sin). In Orthodox teaching, the sin of Adam and Eve damaged the relationship with God, but there was no change to the essential nature of the human person because sin does not have the power to alter God's Creation. The sin of Adam and Eve ushers death into the world.
In both East and West, there is a need for a Savior. In the West, Jesus' death was an atonement for the sins of all of humanity. In the East, Jesus' death on the Cross, destroys death. In the Divine Liturgy, it is proclaims "Christ trampled down death by death". In the East, there is no need for a dogma like the Immaculate Conception because Mary (and indeed all of us) are not lacking in our human nature.
Here is a quote from "Light from the Christian East" (113-4)
"According to Orthodoxy, sin is not an act of nature, but of a person. This correlated with the Eastern Christian understanding of creation: each nature created by God, and each individual which embodies that nature - whether human, animal, plant or whatever - bears within it a logos which impels it to God's service. Further, even after the fall of our first parents into sin and the horrific consequences that arose from it for human beings and for all the rest of creation, each created nature - and thus each individual that embodies that nature - still carry within it that dynamic logos which calls it to its appropriate divine service."
On the topic of Mary, I do believe she was without sin and I believe that, by the grace of God, her logos was most especially attuned to the service of God. My doubts are not on WHO Mary was/is as the Theotokos, but on HOW the Catholic Church teaches about who she was/is. The doubt is on the formulation of the teaching, not the person of the Theotokos.
If I have faltered on explained the Eastern Orthodox teaching, I ask that Orthodox believers fill in my gaps.