mankind is born with a self reliant will, a nature that wantsto have its own way and to sin and disobey God.Perhaps we could look at a few other issues to help.
For example, it has been suggested that Jesus had to be born of a virgin in order to avoid this "sin nature". This suggests that sin is a biological issue rather than a response to temptation based on the desires of the flesh (James 1). Are there any passages that suggest sin is passed down genetically? Scripture speaks of the wicked as being of their father the Devil. Does this mean Satan or his demons actually fathered children (i.e., was Daniel Parker right)?
So the nature of sin needs to be explored (is it an act of the will in disobedience to God or is it a genetic predisposition passed down biologically).
Also, what we are referring to as "nature" needs to be addressed. Perhaps the reason this "sin nature" is foreign to Scripture is how the term is used (Scripture only refers to the "flesh" and the "spirit"). Maybe it is an issue of definitions.
Jesus never had that aspect as part of His humanity.
You seem to be getting hung up on the fact that Jesus was fully human like us, and yet had no sin nature in Him at same time!
Virgin Birth is way for Him to avoid corruption from the fall...