You seem to be contradicting your previous belief.
That is to say he had the same nature as David and Adam. Is that what you believe?
What do you think I have contradicted? Jesus was truly God and truly man, which means he was in nature truly God and in nature truly man.
What I see is that as soon as there was sin there was a savior. He laid down His life right there in Eden where the rebellion began.
But, he didn't lay down his life until his actual death, which was after the incarnation.
He gave up all the prerogatives of God to be our life to give us a needed advantage against our captor.
Again, the Son didn't come to earth and wasn't given for us until the incarnation. That is one of the most basic, fundamental teachings of Scripture. That is what all four gospels show, particularly Matt. 1:18-23, Mark 1:1-4, Luke 1:31-35, and John 1:1-18. Among other NT passages, it's also what both Paul (Gal. 4:4-5; Phil. 2:5-8) and the writer of Hebrews (Heb. 1:1-3) show.
If we are quiet we will feel Him reaching out to the Father on our behalf.
If that can be said, it can only be said of those who are truly saved.
John 3:16 declares that God gave us His Son.
Yes, and that occurred in the gospel passages I provided, not before then.
He was the spiritual replacement of the spiritual aspect of the nature that God gave us which died.
No, he is the propitiation for our sins, through which we are reconciled to God. There is no "spiritual replacement." We were separated from God due to sin and we needed to be reconciled.
After sin we became only flesh, carnal. Without the Son in us we would not have life (1John 5:12 "...he that hath not the Son hath not life."
Yes, exactly, but that does not and will not happen until a person puts their faith in Jesus.
Joh 1:9 The true light, which gives light to everyone, was coming into the world.
Joh 1:10 He was in the world, and the world was made through him, yet the world did not know him.
Joh 1:11 He came to his own, and his own people did not receive him.
Joh 1:12
But to all who did receive him, who believed in his name, he gave the right to become children of God,
Joh 1:13 who were born,
not of blood nor of the will of the flesh nor of the will of man, but of God. (ESV)
Joh 3:14 And as Moses lifted up the serpent in the wilderness, so must the Son of Man be lifted up,
Joh 3:15
that whoever believes in him may have eternal life.
Joh 3:16 “For God so loved the world, that he gave his only Son,
that whoever believes in him should not perish but have eternal life.
Joh 3:17
For God did not send his Son into the world to condemn the world, but in order that the world might be saved through him.
Joh 3:18 Whoever believes in him is not condemned, but
whoever does not believe is condemned already, because he has not believed in the name of the only Son of God.
Joh 3:19 And this is the judgment: the light has come into the world, and
people loved the darkness rather than the light because their works were evil.
Joh 3:20 For everyone who does wicked things hates the light and does not come to the light, lest his works should be exposed. (ESV)
Joh 6:33 For the bread of God is
he who comes down from heaven and gives life to the world.”
…
Joh 6:38 For
I have come down from heaven, not to do my own will but the will of
him who sent me.
…
Joh 6:50 This is the bread
that comes down from heaven, so that one may eat of it and not die.
Joh 6:51 I am the living bread
that came down from heaven. If anyone eats of this bread, he will live forever. And the bread that I will give for the life of the world is my flesh.”
…
Joh 6:62 Then what if you were to see the Son of Man
ascending to where he was before? (ESV)
There are numerous passages which attest to this, but you have also left out an important one, one that forms more of the immediate context of 1 John 5:12:
1Jn 1:1 That which was from the beginning, which we have heard, which we have seen with our eyes, which we looked upon and have touched with our hands, concerning the word of life—
1Jn 1:2 the life was made manifest, and we have seen it, and testify to it and proclaim to you the eternal life, which was with the Father and was made manifest to us—
1Jn 1:3 that which we have seen and heard we proclaim also to you, so that you too may have fellowship with us; and indeed our fellowship is with the Father and with his Son Jesus Christ. (ESV)
Notice that John is speaks of "the word of life," "the life," and "the eternal life," and that that life was made manifest, in the person of the Son.
Also:
1Jn 5:6
This is he who came by water and blood—Jesus Christ; not by the water only but by the water and the blood. And the Spirit is the one who testifies, because the Spirit is the truth.
1Jn 5:7 For there are three that testify:
1Jn 5:8 the Spirit and the water and the blood; and these three agree.
1Jn 5:9 If we receive the testimony of men, the testimony of God is greater, for this is the testimony of God that he has borne concerning his Son.
1Jn 5:10
Whoever believes in the Son of God has the testimony in himself. Whoever does not believe God has made him a liar, because he has not believed in the testimony that God has borne concerning his Son.
1Jn 5:11
And this is the testimony, that God gave us eternal life, and this life is in his Son.
1Jn 5:12 Whoever has the Son has life; whoever does not have the Son of God does not have life. (ESV)
To "have the Son," as John states in verse 12, is to believe the Son of God came in the flesh, embodying eternal life, which will be given to those who believe.
When sin entered He became the Seed of the woman. I believe that every offspring of Adam had the Seed in them to reconnect them to the Father and be able to follow and obey the Father.
That is more akin to Gnosticism than biblical Christianity.
Without the Son in humanity they had nothing in them to desire or respond to God.
Not so. Certain individuals, such as Abram, did worship God and put their faith in him and his promises.
The human race would have perished in the first generation.
Not so. God is sovereign and only lets so much happen. First, we have the account of Noah and the utter wickedness on the earth, so much so that God destroyed almost everyone. That alone proves your position in error. Yet, we see that some, eight people, followed God and whom he saved by his grace. Second, we see in the story of Job, that God only lets so much happen:
Job 1:12 And the LORD said to Satan, “Behold, all that he has is in your hand. Only against him do not stretch out your hand.” So Satan went out from the presence of the LORD.
...
Job 2:6 And the LORD said to Satan, “Behold, he is in your hand; only spare his life.” (ESV)
Even with the Son as a gift to us, the human race almost perished just prior to the flood. One more generation would have finished us off because so many had aborted the Seed due to neglect.
There was no gift of the Son until Jesus was born.