What's the evidence that backs up your scenario?
If you don't wish to type it out again, could you link to where you have presented the evidence before?
We'll have to take it in parts.
The evidence for all this is not easy to get at. It's history, after all, not physics, so it can only be explained via the messy details… you never get an elegant theory and revealing experiment that can show it in an instant.
Going through all that will take some time, but I can take it in parts, if you like.
But first let me note that two of the most important pieces of evidence are, in some ways, invisible… at least at first glance.
They are context and convergence.
The thing about this scenario is that it not only conforms to all the various pieces and types of evidence we have (convergence), but it's also entirely mundane (context) which is to say that there are no surprises here.
For example, if we find letters referring to an American soldier during the Civil War, and those letters tell us that he was a farmer, in his late 20s, a Christian, with a wife and a couple of kids, well, what's to doubt? Especially if unconnected sources agree, and we have photos or other types of evidence that support these references.
However, if we find another source referring to this soldier, and it reports great heroic deeds by him, and yet we find no reference to such deeds in earlier letters by others, and no reference in any local newspapers of the time, and the accounts of his heroism are in some ways contradictory or implausible or if they get facts wrong about the battle, and the author of these accounts is the promoter of a traveling show in which this fellow works as a sharp-shooting act, then we see that source for what it is, an attempt to portray an ordinary soldier as a hero.
That's how textual criticism of ancient literature works, at least in part and as it relates to this kind of question. And doing this work for ancient texts from ancient cultures requires the cooperation of linguists, archaeologists, historians, and other specialists in order to tease out the facts about the texts (who made them, when, where, why, for whom, based on what?) and place them in the wider context of time, geography, politics, and culture.
So, why do we believe that he was a Galilean Jew raised in Nazareth?
Well, keeping in mind that historical evidence is cumulative, and no single piece stands on its own….
1. That what everybody says.
2. There is nothing to be gained by making this claim if it's not true. There is nothing special about being from Nazareth.
3. There are efforts to explain it away.
For example, we find two distinct and entirely implausible stories that arise in the next generation or two after the death of Jesus, which place his birth in Bethlehem in order to conform with a prophecy, and which then have his family move to (or back to) Galilee where he grows up.
The only prooftext offered regarding his origins in Nazareth -- prooftexts are citations of scripture showing how an event comports with prophecy -- is from some obscure rabbinical source (or some such) that is now lost to us, and appears to be rather clumsily shoe-horned in to fit, saying that he would be called a Nazarine, which is a far cry from a Biblical citation saying "he will come from Nazareth".
If Jesus had not been from Nazareth, nobody would have gone to such trouble -- or any trouble -- to explain that fact away. They would just have never made the claim in the first place.
4. Given the politics and culture of the time, it's not at all surprising that an apocalyptic holy man from Galilee would emerge from John's group to gather his own following and end up crucified by Pilate at Passover for preaching that the Kingdom of God was about to arrive and the high would be laid low and the lowly would be exalted.
In short, Jesus being from Nazareth in Galilee fits everything we know, is not in the least surprising, and neatly explains why later Christians invented the particular birth narratives that they did, and why the clumsy prooftext appears.
There is simply no good reason to doubt it, and every reason to believe it.
OK, got obligations to keep, more later.