You raise a lot of good points, Dagoth Urist!
At some point I'll try to answer your questions and consider your ideas, but I don't really have time for that so early in the morning.HERE WE GO
Do you want to draw parallels to the Christ, someone else, or do you want to keep the saviour completely without influence of real-world messiahs?
well he's quite obviously a christ figure (with some Joan of Arc elements), but if you know any other messianic figures I could draw inspiration from, that'd be great. You know, to add some variety to his influences.
The Age of War, beset by the goblins worshipping the Black Goddess, if I understand it correctly? And barbarian hordes too, it seems.
The black goddess worshippers were human - they were a separate force from the Goblin Hordes.
AGRESSORS DURING AGE OF WAR: Human/Dwarven Barbarians, Goblin hordes, Elven Cannibals, Human Cultists.
The Saviour's teachings promoted reason and tolerance in a Crapsack World, am I right? Did he value peace highly too?
Yes, peace was always his intended goal. He may have been a bit flawed in his methods, though.
I think it looks like he was partly a religious leader, partly a military one. Not that there's anything wrong at all with it, I'm just notifying. Then again, The God and what he represent are in that same duality, so...
Pragmatism is a big part of his leading style. He knows that while he can convert many to his side through teaching, there are some who would prove unreasonable and must be dealt with through military action.
its a nice touch that it was even a bit of an instruction manual for life.
I tried to keep it away from being all about superstitious religous practices... the Saviour was only teaching the intelligent races how to survive and prosper, not how to live their personal lives (aside from fundamental guidelines about courtesy and tolerance, there's no list of sins or elaborations of right and wrong)
Are there a lot of different variants and dissidents of the faith? Logically, it should; unless there is a strong organization that regulates what can be said and what cannot. Since the book was incomplete, there should be several ways to interpret the saviour's tolerance and reason. Even if there is a strong "church" that goes down on rogue upstarts; even if there is, there could be dissident factions that "spreads the truth underground".
You could say there are two general factions of man: those who follow the saviour's lifestyle of reason and rationality (but do not follow his word religously), and those who actually revere the saviour as a divine being (these being the ones who thought up his divine father and all those fire-based traditions)
there is really no regulation on who can believe what. Something like this would be hard to manage in-story seeing as humanity coexists with elves and dwarves, both of whom have different religous beliefs! (not to mention any remaining humans who choose to follow "pagan" beliefs)
Still, was it just an age of peace, or were there more "modern" improvements that the epithet suggest?
Yes, it was basically an age of peace with modern improvements. (there is limited understanding of gunpowder weaponry, for one)
Why exactly did the dwarves and elves leave the Keep, why not live with the humans instead?
It is simply their way - elves and dwarves, being very long-lived races, are not all that comfortable with making drastic changes to their living style. Elves live in forests, humans live in cities, dwarves live in mountains - that's just the way it's always been.
Did a few elves and dwarves actually stay with them?
Yes. See the "races" category in the original post - it describes "hill dwarves" and "half elves" as dissidents from their race who chose to live as humans.
Did the construction of the Keep have a more pragmatic purpose?
It was essentially a centerpiece for the alliance to build their new society around - the towns surrounding it serve as trading hubs, among other purposes.
The map you supplemented in the first page of Effigies, does it show the entire continent?
I probably should have elaborated on this earlier... no.
the actual continent is far larger than the area inhabited by the remnants of the alliance. The kingdoms of the mortal races once spanned a continent about the size of the americas - but so many died during the age of war. The sparse populations left over are pathetically small compared to their size during the age of peace.
Right now, the combined numbers of elves, dwarves and men barely reach 100,000. It is a bittersweet existence: the world is at peace, but so much has been lost to attain that peace. Only a tiny percent of the continent is civilized - the rest is covered by "the great wild", which is a lot larger than the chapter one map implies (most citizens are unaware of how big the world really is)