I will update this post as soon as I can, in order to answer all your questions (Thereafter, I will provide a file with all the answers in the first post) :
1. Addressing rumors and complaints that reviewers had: Is Yuna cold to Tidus? Does she seem less in love with him than she was in X and X-2? Are the rest of his friends cold or unwelcoming to him?
Yuna is not cold to Tidus, it's just she thinks about what she must do in the future (Working for Yevon or not ? etc.). Tidus is a little hard with her about this, so it does not help to defuse the situation. But his friends are very affectionate with him, his mind is just a bit dark and thereafter he becomes angry. Wakka is gentle, Rikku is gentle (but she has an argue with him), etc.
2. More rumor clearing up: Is Tidus unusually sexual? Follow up question: Did they or did they not have sex on the boat? And is that why the boat crashed??? xD
Tidus is a bit... flirtatious. Well he's a man. But he doesn't think "I want to do her !". He just want some good time with her : for example, they kiss, this kind of things.
I can't say if they have sex on the boat, there is an ellipsis. But that's not why the boat crashes. The boat crashes because of the violent sea, but... it seems the cause was a bomb in fact... because Tidus smells gunpowder at this moment. I don't know more about this.
3. How does Tidus die and how is he revived? I know we've cleared up how he died, now, but some more detail would be nice!
Tidus dies because of the ball which hits him on the back (as said in the previous topic, the translation is correct). This ball is a bomb from Zanarkand (see also the rundown "1000 years ago"). About his revival, Yuna gathers his pyroflies thanks to her powerful will. It's named "beckoning" in the previous topic. Tidus becomes an "incarnate spirit". Thereafter, Yuna is woken up by Tidus. I don't have more to say.
Just so you know, I think Tidus was murdered and I will explain why later (too long, too complex).
4. More explanation of Yuna losing her memories and how she got them back would be nice, too!
Read "Ifarnal / Yuna 1st conversation". Then, you need to know that Tidus and Yuna meet Kushu (as an aeon) soon after but their conversation becomes "weird" (it is very difficult to explain, I plan to translate this moment) and Yuna discovers that Tidus is an incarnate spirit.
5. Wtf is going on with this Sex Fayth method stuff?! Is it real?? If it's not used by Yuna and Tidus in the book, why is it even mentioned at all? Did Ifarnal and Kushu even know each other before they had sex?? Because FFX made a big deal of 'you have to have a strong bond to create the Final Aeon'. Is sex itself, regardless of whether or not you actually KNOW the person, considered bond enough, haha? That's taking the 'bonding' part quite literally, isn't it? You don't have to actually have an emotional connection, just need to have... connected bodies. xD I'm just curious because this little tidbit about old summoning methods is interesting, but seems out of place in the generally rather PG Final Fantasy world.
I need your attention here : Kushu is found half naked in Ifarnal's room, but nothing allows me to confirm a sex scene ! Ifarnal's fayth method could only be some... "foreplay". This point is very difficult to elucidate ! When Ifarnal hands down this knowledge to Yuna('s mind), she blushes. But she is not outraged. So maybe it is really just "foreplay".
6. What is the significance of the island, and the dead summoner(s?) who inhabit it? What relevance do they have to FFX/Tidus and Yuna/the plot of the novel/games? Basically, why is Nojima telling us their story, is what I want to know... o.o Surely there must be some kind of 'lesson' or significance to be had from their story, right?
The island is a summoning from Ifarnal ! It's about the Besaid from 1000 ago ! If you want to know more about this island and the connexion with Ifarnal, read the rundown "1000 years ago". Ifarnal uses a lot of fayths to make it appear.
Ifarnal wants to send Kushu into the farplane, because Kushu's body remains in Besaid Island (the real one, not the summoning), but he doesn't know where her body is exactly. So... Tidus and Yuna' arrival is a good opportuny... (It will merge with what I said before about Tidus being possibly murdered)
7. Also, if you want to fill us in on what their story even IS, that'd be cool, too. xD
I will provide a file with details about the global story. Just let me some time
8. Ifarnal "had children as an unsent". Does it say (or hint at) who these children are? Was it/they conceived when Kushu and Ifarnal made the aeon, or is it Ifarnal's and someone else's? I'm curious as to whether the child was born 100% unsent or just half... or... is it some kind of special state of being because the Sex Fayth method... just wondering what it means to be a child of an unsent. o.o Also whatever happened to the child?!
TUTUTUTUTU FALSE INFORMATION DETECTED !
Ifarnal did'nt have children. But Briah had ! In fact, He had one daughter named Luchera. But her name was changed to Mohra because under pressure from... Bevelle. It is a bit strange when you know people from Bevelle's side took names from divinities like this "Luchera" (Kushu, Ifarnal, etc.). Briah's wife is named Meroh, someone normal. So no sex-method. Unfortunately she died from torture. The culprit is... Bevelle. Bevelle wanted to know how she knew about "Anli's eye", a star. Because Anli is a divinity too, like Luchera. So it seems Bevelle has some shame about its past... At the end, Mohra died of old age.
9. "If either figure out, the process would be "undone"', in reference to Tidus' revival. So, at the end of the novel... what exactly do they and do they not remember? Do they remember the things on the island that happened before and AFTER the revival, just not the revival? Or do they not remember anything at all from the island? And does 'coming undone' mean Tidus would die again, or... what?
They remember everything about the island. Only the death's moment remains unknown to Tidus (Yuna remembers it).
'coming undone'... Well even for me it is difficult to find an answer for now
10. What is the overall feeling at the end of the novel? Are they happy, sad, hopeless, hopeful? I know you said the very end is the Perfect Ending, but what about before that? I'm just trying to get a feel for what the message/point of this novel is...
At the very end of the novel, Tidus seems to be enthusiastic, he wonders about his condition but seems happy. Yuna detaches herself a bit, she is very worried about Tidus and his state (incarnate spirit).
Before this ending, Tidus and Yuna witness Briah and Kushu's meeting. It is very beautiful but very strange and very sad too. Tidus tries to prevent Briah from going (into the farplane I suppose). Yuna barely speak. It is better to read this moment in order to understand it well. Kushu leaves (with Bria I suppose too) at the end.
11. What connections does this have to the Audio Drama? It introduces beckoning, yes? Do you think any of the events in the novel foreshadow or explain the events of the Audio drama?
Yes, it introduces beckoning. It explains why Tidus seems weak. About the return of Sin... I wonder who wished for this.
12. Oh, yeah! What ever happened to the Briah person?! Do they say? Are they on the island, too?
As you know, Briah is in fact Valm. So read the rundown "1000 years ago" to know about his past. Briah's memories were constantly erased by Ifarnal each time he was on Besaid or each time he remembered Kushu. But his memories come back when he meet the Al Bheds (Rikku, Shinra, etc.)
After some events, he meets Ifarnal and fight him. Thereafter, Ifarnal dies of a bomb (like the one for Tidus). To know what happened next, read the answer to the question 10.
Also, thank you sooooooo much for doing this! Seriously! Even if it turns out I don't like the details, it will give me so much comfort to finally have them. As a huge fan of the game, it's been so terrible being in the dark about all this stuff.
You're welcome !
And for the record if anyone ever hears of or wants to embark on a project for the effort of a full translation into English, I'd do my best to offer donations and such!! I've seen a few projects like that for other novels/Ultimanias etc. on forums, so apparently, that's a thing that people do, right?
If I was good with english, I would have translate the novel (for free), but unfortunately I am not