And on to the questions!
No – the epistolary friendship between Horion and Pan Szeric wasn’t known or comprehensible to most of his clan allies. And “Eye” is the way some high-country clans refer to their leader, with no implication of spying.
A few Abhumans choose to look mostly human, but they have to be thick-skinned to put up with the scornful assumption that they’re incapable of understanding the strengths of their Gara’u animal. “Werebeast” just means human-beast, and applies to people at any stage of transformation. There isn’t a perma-lock on change.
Maybe this was a typo–not sure why the landlocked faction would seem the most likely to make a massive naval innovation? Regardless, no, I don’t plan to have submersibles or scuba kit in the gameworld.
They are in Kleitos’s power in that he knows how to do them, but it takes Ward-scale logistics and preparation. He won’t be doing them off-the-cuff.
Hugely variable. They’ve been subjects of a common ruler for nearly six centuries, with high rates of intermarriage, and the big Westriding Houses have been some of the most prosperous and powerful outside of Karagon. But with lots of power and wealth concentrated along the coast, resentments have inevitably built up among the less well-connected peripheral aristos, especially after the Rising reduced loads of small/medium Westriding Houses to genteel poverty. An Earlund movement could crystalize a lot of those resentments, especially if it looked like Loyalists were going to keep a lock on power in Grand Shayard.
Ester Cabel was betrayed by a Westriding noble. The Cabelites don’t differentiate between aristos on the basis of geography. (And most of them aren’t familiar enough with “Brimlund” to really feel the difference–it’s a yeoman-driven movement, and they travel less than any other social group in Shayard).
That’s how it looks to the eyes of faith – good role-playing. But even if you fought off the army sent to destroy you in the wilderness, that still leaves you miles from the point where any noble in Grand Shayard would look at you and think “they’re going to beat the Thaumatarchy”. Even sympathizers would still see you as a helpful distraction off on the fringes, depleting a bit of the Hegemony’s strength, rather than the core rebellion. Change comes from power centers, not from the periphery, everyone knows that! (Or at any rate, just about every noble believes that.) And unsympathetic nobles like the de Firiacs wouldn’t even grant you that much respect.
Fortunately, this doesn’t make it impossible to marry S – who’s already defied their parents’ wishes in an even more fundamental way by turning rebel. The vision of a proper, ordered courtship S ends up settling on won’t involve parental permission.
The ability of anyone to lend money to any faction is going to depend on the broader anarchy level. We’ll see how it goes.
Oster founded and built the port of Shayard; Samena was more of a conqueror than a builder, and didn’t slap her name on the places she conquered, Alexander-style, so I’m not sure she has any cities named for her.
That’s not a question I’ll be answering until we start playtesting Game 5, I’m afraid.
I’m also not going to respond to questions or speculation about the Gryphon claimant with ancient roots, though when G2 Ch4 is ready for review next year, it should answer several of your questions.
Likewise for Teren – they’ll become clearer in Ch3, and you can tell me which if any fictional counterparts you think they most resemble then, in their ruthlessness or romance.
There are two flashbacks, one aristo, one helot, seeing the same masque from quite different perspectives. (I only had to write in terza rima for the aristo version.)
Fornication is kind of its own sin in the gameworld – no one really considers it fraud or treason, except by slightly over-thought analogy. As in our world, most humans have an appetite for hooking up with more people than is good for them. The monogamous “myth of halves” doesn’t deny that, but just says that it’s a sin to indulge that appetite with anyone but your other half.
Also like our world, there’s been some fluctuation between times/places when the “other half” was taken, definitionally, to be your spouse–if you found you’d married the wrong person in error, tough luck!–and more “courtly love”-esque settings where there was cultural sympathy and glamor around the idea that many people only discovered their other half once they were married to someone else, and could be expected to outwork that all-important relation in more or less adulterous ways. There’s some of that diversity in the gameworld today. In the Rim of your youth, the expectation is strict chastity rather than courtly longings; in the coastal culture that extends (with significant variations) from Erezza to Grand Shayard, it’s more common to see variations on the amour courtois ideal.
Depends on how you encouraged it, and with whom. Not all pro-natalist policies are experienced as pushing people to mate against their nature. Killing off people who don’t reproduce is very different from rewarding people for every kid. Regardless, once Theurgic agriculture starts crashing, you’re highly unlikely to need natalist policies in the gameworld.
In-vitro fertilization has not been developed and I have no plans for it to be.
It should be possible to end up with a merchant-led alliance ruled by a council of citizens, yes. I suspect it will feel somewhat different coming as it does in the immediate shadow of an imperial collapse; the real Hanseatic League united cities with long-established rights and autonomy, rather than ones coming directly out of centuries of autocratic control.
Probably. 
Not immortality, but significantly extended lifespans, yes.