It is not that simple at all...
And that is a very nice and thorough story line except that it isn't true. You clearly believe in a literal "fall of man" although you railed against me for doing so as well. This being the case, the physical universe stands in evidence against your story thus making it moot and nothing more than a simple tale.
Moreover, even accepting your premise, the results are irrational. If God is a Father then "who can separate us from the love of " God? If, as your story purports, man is spiritually broken in some fashion and therefore "alienated" from God it is "sin that separates us" from him and the way that any normal human being regains a right relationship with one against whom he has sinned is to ask forgiveness and for the offended to simply forgive. Nothing more. Nothing less. Sacrifice does not enter into the equation. All that is required is for your God to forgive people. Period. But this is not something that He is willing or able to do.
But your story tries to take things a step further. Not only is it required that one has to accept the conditions of a perfect human sacrifice (something that God abhors in the OT) but your book states that those who do accept this are "a new creation. The old is gone, the new has come." Your religion would have us believe that just as the first Adam was sinless and that his spiritual condition changed as a result of committing a sin, so too those who accept the "free gift" ought to be fundamentally changed so that they are again perfect as Adam was. But this is not so. Indeed, the divorce rate among Christians is 60% (
ref). Christians are as prone to "sin" as anyone else. In short, there is no evidence for this later claim of Christians being "a new creation." Evidence against this claim is easily measurable whereas there is no evidence to support it. How then can you expect anyone to believe you about things that are ethereal and unmeasurable such as your story of the "fall of man"?
Finally, the physical completely eradicates the Christian idea of a "sin nature" etc. For example, there was a time in Judeo-Christian history when people were considered to be "possessed by a demon." Today, there are no such claims because we know that mental illness, epileptic seizures and other conditions of the brain are the causes behind the behaviors that were once attributed to demons. And the cures are physical as well. Science has found solutions to those conditions that Christians of former times attributed to spiritual causes. How can that be if there really are demons and a spiritual world plaguing us?
There is no lack of evidence of a growing number of Christians who suffer from depression and who are finding relief with the use of antidepressants. If the spiritual life of an individual has any bearing on their mental status, how do you explain these things?
The reality is that all those conditions that were once considered to be spiritual in nature (possession, lust, anger, hate, etc) in fact are physical conditions. Some of these can be treated while we have yet to discover treatments for other conditions. What will happen to your myth when science has effectively mastered the human mind to the degree that all those things that were once thought to be spiritual have been effectively managed through physical means? Certainly they cannot be managed through "spiritual" means as history has demonstrated quite clearly.
It's all nonsense and the only hope for the human race is to recognize that we are simply physical beings who behave in certain ways (whether because of traits that were valuable in our evolutionary past or what have you) and that the means of changing ourselves as a species lies in the physical sciences and not in the hocus-pocus world of never-ending ethereal debates about "interpreting divine revelations" and whatnot.
In short, Jesus has failed to save anyone from the "sin" that allegedly alienates man from God. So has every other religion that believes that there is an alienation between God and man. That people still buy into it is amazing but there are a growing number of people who have shunned religion (
ref) and that, to me, is a wonderful thing.