I hardly see why this is a necessary conclusion. It's based on the assumption that the "default" is union with God...but why is this assumption made?
Sin brings death, lack of union with God.
It's also based on the assumption that sins are reducible to "acts", but this is a very deficient view of "sin" (IMO). Sin is undoing of good, the undoing of the will of God. It is not "some-thing" in and of itself, but is only manifest in so far as it is the diminution, or negation, of the good.
Sin is an act that goes against the will of God. There is sin in general, but I was referring to the specific instance of committing that generality "sinning"
This logic doesn't follow. If a person were never separated from God, why would they need salvation in the first place? Salvation suggests being saved "from" something, correct? So if a person does not need saved "from" something, and is also united with God, how is this "salvation within us?"
Above, you claimed a person isn't born in union with God, here you claim why would a person need salvation if they were never separated? If someone was born sinless it would be something within their ability to never be separated from God (sin). Someone could keep themselves in unity with God hence never needing a savior this means Christ's salvation is only a secondary act following peoples inability to live in God's laws, not a necessity for every human from birth.
We are born into a sinful world and are shaped and formed by our parents and society to be sinful people. Obviously, we all reap the effects.
This is unbiblical. You have yet to produce any evidence for your view. The only reason we need a savior is because the outside influence of the world will force us to "depart from good?" what a limited understanding of redemption.
Blame? Sinfulness is not blame, it is a orientation away from God, an animosity toward the will of God, a fracturing in the human-divine relationship. It has nothing to do with biology, and your thinking comes crashing down the moment one considers whether or not Adam is a real human being.
"Sinfulness is rebelión against God, and it is unrightousness. Sinfulness is what forces each of us to deserve the judgment of a righteous God who can't defy His own Character. Every person alive deserves his judgement there is none righteous, not none before they commit departure from good, but none.
Romans 3:10 As it is written: "There is no one righteous, not even one;
The logic doesn't follow. If we have inherited sinfulness biologically from Adam, why have we not also inherited salvation from Christ biologically, since he is the New Adam?
This is a blatant straw-man, first Christ never had any biological offspring. Second, The father is just, Christ atoning for us on the cross was the only way for us to be redeemed from our fallen state. God can't defy his own righteousness, he needs payment for our sin, Christ was the only one who could make that payment. It is only in believing in His works that we are regenerated, and sealed with the Holy Spirit unto salvation.
All of these questions aren't really related to the question at hand, which is why was Christ sinless. The Scriptures make it very plain that Christ was sinless not because of his biology, and not because of the virginity of his mother. Rather, he was sinless because he did the will of his Father. Look it up.
This exegete is operating on the false premise of humanity being born sinless. You keep saying look it up, how about, you show me the section of scripture you interpreted to fit your theology.