If it's any consolation I spent eight months of last year reading the sources for the Fourth Crusade and Fall of Constantinople, and then trying to reconstruct from things like the
Chronicle of Morea the subsequent political situation in the former Byzantine Empire 1204-1230 for something I was working on. I share your pain!

I must say that the secondary literature on the details of the Byzantine successor states and this period is almost non-existent, at least among Western European historians - it makes British sources on the French section of the front in World War one look positively abundant and useful! - so it was an excruciating business. I'm currently writing on another topic just as difficult with regards to sources, but I had better not say what until it's published.
Oh yes, constraints. Very quickly, without references and warning this constitutes what Wikipedia might call "original research" as I'm not sure how far it reflects the current academic consensus - the oral stories preserved about Jesus are clearly NOT the totality of the pericope circulating at the time of the writing of the gospels. In fact, a couple of the gospel authors make this plain, and say so explicitly. The stories we have reflect the
sitz in leben of the Early Church - they were preserved as useful to some problem or teaching the Church wished to express - that much is uncontroversial.
I'd go further, like a bus load of Merry Pranksters heading east to Millbrook. We can tell that in fact the authoes also shape their material in line with their own theological spin - no surprise there - and that they have there own literary conventions or way of writing - compare and contrast the depiction of Jesus in John with the "Messianic Secret" motif so obvious in Mark. Still, even beyond the selection of material by the authors for whatever reasons, it is highly likely that by the time the Gospels were written the early Christian communities (I don't think Early Church is really an appropriate term though I often use it through sheer laziness) have actually got a standard by which stories about Jesus are judged - the Apostolic Acid Test if you like.
The Apostles, the inner circle who were there from the beginning, seem to have held considerable authority - I can only think of non-apostolic three figures who may well have been as influential. One I only suspect - Mary the mother of Jesus. One we can clearly see - James, Jesus' Brother, Head of the Jerusalem Church.Both are clearly authorities in their knowledge of Jesus.
The third was Paul, or Saul if you prefer. And here we hot a massive problem - because Paul was a highly influential figure, a great theological figure, and clearly NOT an apostle. In fact the other apostles question his teachings and it would seem likely by various things he writes, his very write to teach.
Because Paul was not there. He missed the ministry, he missed the Passion, and he missed the Resurrection appearances.
So from his writings, especially in Galatians, we can see the conflict which culminates in what is often called the "Council of Jerusalem" in 62 as i recall? Paul stands sort of half way between the Apostles and modern Christians - the Apostles believed what they had seen - but Paul had a spiritual experience of the Risen Christ,as you rightly mention (though it's far more complex than it first seems and will form part of the discussion in my next post, replying to your former points I still have not got round to!). So Paul makes himself a new type of apostle "as of one untimely born" as he says, and the Church accept him - a bit warily perhaps - but we notice something very interesting in his writings in the seven authentic Pauline Epistles.
Paul is very scanty on the Historical Jesus, in terms of biography. That si not to say he gives us no information ---as is often claimed -- about the Historical Jesus, for he does and I can summarize it here with quotes for anyone interested. However generally, even when his argument would be strengthened by reference to the biography of Jesus, he shys away. Why? Doherty and others who believe Jesus was fictional cite this as sinister - but I see it as perfectly understandable. Paul has been pulled up for teaching without Apostolic authority - he is talking about someone he never knew in the flesh. If he tries to draw upon the liefe of Jesus, he can easily make mistakes, or include claims that are falsifiable by the still living witnesses - the Apostles. So he avoid the subject, and works theologically, and through his own experience. He is not afraid to argue theology with the Apostles - but he has ot be careful to never overstep what he actually knows about Jesus - and we see this reflected in his writings.
What does this tell us? That there was in fact a process of authentication of material going on - that there is an Apostolic tradition, that is used ot test the pericope. As the Apostles dies off there is a need for biographies which reflect the apostolic teaching - but now that teaching is disseminated in various communities around the diaspora and the Eastern Mediterranean, so the gospels are composed, and probably read by those taught by the apostles - a process we can see continuously as primitive Christianity begins to definie itself as distinct from Judaism and from the various gnostic versions of Jesus. This claim to apostolic authority remains central to the early Christian communities - and so it forms a constraint in that one can to teach contrary to the apostolic "memory". In areas not covered by the Apostles - and i strongly suspect the birth as one - stories could be accepted, and contrary versions accepted - but the core events have to refer back to stories told by those who were there. A theological system of checks and balances are in place.
Yet even in the Resurrection accounts, different Apostles had given different accounts one assumes, and we see a complex patter n emerging, where seemingly contradictory accounts - who was first at the tomb? - emerge in different communities. I find this quite understandable - the writers were drawing in each case on what they felt was the most reliable source - hence the disagreement between them. If the transmission was as simple as say Mark wrote, then Matthew copied him then Luke copied Matthew, then we would expect a broad agreement. If the whole thing was a fiction, we would expect agreement, because the story would develop, and change, but you would be careful to get your key details accurate in your spin on it. Here however i suspect we actually see the problem of the apostolic authority - the apostles
kerygama, message, was very much focused on what to do and how to receive the faith, and the historical part of their accounts while treasured reflect a number of revered witnesses quibbling over what really happened twenty years before. So high was the regard hel for them, the inconsistencies had to be accepted - because they were depsite the problems better than the competing teachings in circulation which while "smoother" disagreed with the Apostolic accounts?
Dunno. I'll reply to your other bit later if i can. Hope not too way out
cj x