No one denies that Jesus is fully human, but without sin. What I am stating is that Jesus, as the 2nd Adam, comes into the world like the 1st Adam, without the curse of Adam upon him.
I think the reason we do not see eye to eye here is related to the Fall.
If I understand you correctly (and please let me know if I do not- my intent is to let you know how I am taking your response and not to put words in your mouth) you seem to believe that when Adam sinned a change somehow occurred in his DNA
I do not believe that Adam's nature changed at all. Of course, this may depend on how we define "nature", but I think we would disagree if this were fleshed out.
I interpret Scripture as indicating that Adam was created and then (after Adam was created) God took Adam from the location where Adam existed and placed Adam in the Garden of Eden, where Adam existed in God's presence.
I believe that a few things occurred because of Adam's sin.
1. Adam's (and man's) eyes were opened to and Adam "became like God", to "know good and evil".
2. Adam would have to work the ground.
3. Because of Adam's sin, Adam would die ("for dust you are and to dust you will return").
As far as I can tell (from Scripture) these are the changes that affected Adam directly.
Other aspects applied to the Serpent and to Eve. And God Himself subjected Creation to futility (in hope).
Nothing in Scripture indicates an ontological difference between Adam and Jesus insofar as humanity or human nature is concerned. Nothing in Scripture indicates that we differ from the 1sr Adam as far as our nature's are concerned.
My conclusion is that if we, prior to being born of the Spirit, were taken into the Garden instead of Adam the result would be the same. I believe Jame's description of how sin manifests applies to Adam before the Fall (it is an eternal truth).