I agree. I understand the use of the word "one" pretty much as you do.
You're not exactly making sense here. You're saying that we all have a sinful nature but that neither Adam nor Jesus did, that both of them came into the world without sin. I believe that each and every one of us came into the world without sin. We are predisposed to being sinful, but we are not guilty of anything until we actually do wrong. And by the time we have reached a point where we can understand the difference between right and wrong, we will have done wrong, and will continue to do wrong. The pull of sin is simply too great for us to withstand.
Gen 1:31,
And God saw every thing (including Adam) that he had made, and, behold, [it was] very good. And the evening and the morning were the sixth day.
Adam was created perfect. Part of that perfection included free will. Apparently God didn't think it good to make robotic people. Part of Adam's perfections included the ability to obey God or not. God was forthcoming when He told Adam what would happen if he disobeyed (Gen 2:17). Adam disobeyed anyway, and lost his God given perfection. That imperfection was transferred to all people via seed, which seed was corruptible. That is why all die.
There is a verse that speaks of the two types of seed in 1 Peter.
1Pet 1:23,
Being born again, not of corruptible seed, but of incorruptible, by the word of God, which liveth and abideth for ever.
The seed we get when we were first born is corruptible because of Adam's sin. Genesis makes a point of saying that a seed contains the very nature of the father which gets passed on to the son. If Adams seed was corrupted, then so was Seth's, enos', Cainan's, etc, right on down to you and I. The first few chapters of Romans spells out in some detail why we have this sin nature, which, as you said makes it impossible for anyone with corruptible seed to live a sin free life. Dog's bark, cats meow, cows bellow, and people sin.
But, unlike every other person, including Mary, Jesus did not inherit that corruptible seed from Adam. His seed came directly from God, what you call the immaculate conception. That term is not actually in the scriptures, but I suppose it carries the same idea. Thus, Jesus, just like Adam, started out with innocent blood. But unlike Adam, Jesus never disobeyed God and his blood remained innocent. Judas understood that.
Matt 27:4,
Saying, I (Judas) have sinned in that I have betrayed the innocent blood. And they said, What [is that] to us? see thou [to that].
The Passover required the sacrifice of a lamb
without blemish. Jesus, himself without blemish, thus qualified to be our Passover lamb.
1Cor 5:7,
Purge out therefore the old leaven, that ye may be a new lump, as ye are unleavened. For even Christ our passover is sacrificed for us:
Now you're insisting that Jesus is not divine, but fully human (if I'm understanding you correctly). I assume this is because He was conceived by and born to a mortal mother. Since you're not Catholic, you apparently don't believe in the Immaculate Conception, which states that Mary, like her Son, was free from "Original Sin." If Mary was a mortal like the rest of us, Jesus Christ, like all of the rest of us, was also a descendant of Adam. And who exactly do you believe His Father to have been, if not God? I'm simply asking you how a man born as a human being to a mortal mother could be any different from any other man unless His Father was divine and He shared in His Father's divinity (which I believe was the case).
With the exception of Mary being without sin, I think I've shown that what you said is in perfect alignment with the scriptures. Since Jesus is called "the son of God" almost 50 times in the scriptures, I'd be a fool to say God is not his father. I think you misunderstood. Jesus did indeed possess the nature of his father. Every son shares in the nature of their father, so that's nothing unusual. Of course the nature of Jesus' father was different than the nature of my earthly father. Going back to 1 Peter, it is clear that the seed I got from my earthly father is corruptible, whereas the seed I got when I was born again is incorruptible.
My belief is that He inherited His mortality from His mother, a mortal, and His divinity from His Father, who was God. He would therefore have both the qualities and characteristics of both of His parents. From His mother, He would have received a mortal body, subject to pain, disease, injury and death; He would also have received from her the ability to be tempted and the ability to sin. From His Father, He would have received the ability to "have life in himself," i.e. to have power over death, the power to "take [His life] again" after having laid it down. Speaking of "big deals," that's a pretty enormous one. How many men like you and I have that power? Only a Deity could do that. And acknowledging that power which He had in and of Himself, is giving Him the credit He deserves.
It wasn't necessary, indeed not possible, for a god to redeem us. If you read Romans you will see that sin came by man and it had to be a man who redeemed us. It took another man to die with innocent blood to redeem us. While Jesus did have a divine nature because his father was God, it didn't actually make him God. We are born again with the same seed Jesus started out with. We are born again of incorruptible seed, which gives us the same nature Jesus inherited from his father.
I don't get your point of your question here. Yes, the Plan required a Redeemer. It wouldn't have mattered whether Jesus Christ came down to fulfill that role 3000 years before He did, when He did, or 1500 years later. He was the "Lamb slain from the foundation of the world." He alone could do this because He alone was perfect, as His Father was perfect.
God never forces people into anything. He is not interested in robotic worshipers. The only thing He could do was speak to mankind. That would be the Old Testament. Jesus had something real interesting to say about the Old Testament scriptures.
John 5:39,
Search the scriptures; for in them ye think ye have eternal life: and they are they which testify of me.
When Jesus said this, the only scriptures God had given to mankind was the Old Testament. In other words, the subject of the entire OT is Jesus. They explained exactly what the redeemer would have to do to redeem us sinners. Before Jesus came on the scene, lot's of people read them, but nobody was able to actually follow them and thus become the redeemer. When Jesus was born he, like the rest of us knew absolutely nothing about anything. His mind was a blank slate. He had to learn about life and God the same way every other man learns, by being taught things and by study. Jesus studied the scriptures and realized who he was and what he had to do. He could have said, "yeah" or "nay." Like every other man he had free will. But as I said above, unlike every other man, Jesus had innocent blood and thus had a chance at following God's will to the jot and tittle. As you know, he went with God 100%.
The reason God had to wait was simply because He had to wait until Moses came along so He could give him part of the story. There was simply not anybody before Moses who believed enough to write what God told him to write. In a similar way, God had to wait for every writer of the OT to come along so they too would believe enough to write the words. Those words were Jesus' instruction manual. If Adam had enough believing, God could have given him the entire OT which Seth could have possibly read, understood, and obeyed. Then Seth would have been our redeemer. As it was, it took a long time for God to convince enough people to believe enough to carry out His plan. That's the real genius of the "logos" of John 1:1. The word "logos" means a plan of action or a reason for why somebody does something.
Are you saying that God convinced Jesus to do what He did, and that this happened after He was born, and that this role was not His in the beginning? Wow. I just can't buy that. Sorry. I believe that Jesus Christ was with His Father before our world was ever created and that He, in fact, created it under His Father's direction. I believe He was chosen before the Creation to be our Savior, and that despite the fact that He had it within His power to refuse to do His Father's will, He could have reneged on His promise. Rather than do so, He willingly gave up His life for us, proving that He and His Father were, indeed "one in will, purpose, mind and heart."
Not exactly. It was Jesus role from the beginning, but whether of not he carried it out was not known until the end. Jesus could have sinned at any time in his life and thus pollute his blood and disqualify him from being our Passover Lamb without blemish.
I have met very few Christians who understand that Jesus could have failed. God gave Jesus the same free will He gave the rest of us. Jesus was no more robotic than the rest of us. It's a good thing Jesus aligned his will with God's will 100% of the time!
Jesus was with God in the beginning in the same way you and I were with him.
Eph 1:4,
According as he hath chosen us in him before the foundation of the world, that we should be holy and without blame before him in love:
Well that ought to put a spring in your step!