Hi guys, really late to the party, but I'd just like to thank you all for translating and making this accessible to us.
I've read whatever's up at the moment, and here are my two cents:
Lulu and Rikku's behaviors don't actually bother me that much. Lulu has never been a very warm and friendly person to begin with, and her insistence at Tidus going to help set up the party could be seen as her trying to assimilate Tidus back into Besaid. After all, imagine how the Besaid villagers must feel-- this guy who disappeared two years ago at the beginning of the Eternal Calm, presumed to be dead, suddenly appears alive at their beach, and he has some sort of relationship with their beloved High Summoner. I'd imagine that it would be likely that the villagers are wary of Tidus. I'd also consider how unfriendly they were towards Tidus at the beginning of FFX. Sure, not all the people on Besaid Island were unfriendly, but given that their traditional beliefs (I know, Besaid appeared to align itself with the Youth League in FFX2, but they were never all that political? The only visible representation of this is in Beclem, but even then it largely became more of a Blitzball training thing than real political alignment like the issue in Kilika) and how Tidus completely disregarded that during his brief stay in Besaid, their cautiousness around him seems likely.
Sorry, went off tangent there a little-- back to Lulu. I believe her comment regarding her marriage with Wakka was merely a joke of sorts; she does this a lot in the game as well. Rikku has also always had some sort of sibling rivalry behavior going on with Tidus, although we don't see it much. She's also very jumpy and restless. I don't think she was truly angry when she accused Tidus of not listening to her; based on her overall characterization I would say that's just how Rikku acts, which is seen throughout the course of FFX2.
The entire thing with the elders and Yuna does bother me a little, given that there didn't seem to be much of this issue throughout the entire course of FFX, X-2 and the Eternal Calm cutscenes. The only examples I can think of are perhaps the marriage proposal brought up by Wakka to Yuna during the Eternal Calm cutscenes-- in that, it sounds a lot like Wakka deals with the elders for her. I guess it's not entirely implausible that Yuna is held up by these nameless elders; sure we don't see it in the games, but Yuna does at times have this sense of apprehension at returning to Besaid in FFX2. I don't mean that in a bad way: just as she said that she 'felt like a runaway child coming home', it's almost as if she expected to be chided. Considering that she was pretty much raised by these temple elders, it would make a lot of sense that she defers a lot to them. In FFX2, apart from the mission involving the fiends coming out of Besaid temple (and in that one, everyone in the temple was evacuated, so...), there was really no other reason for Yuna to go into the temple. Also, when Yuna was to stay over in Besaid for a night, she stayed in Lulu's house, and not the room in the temple as stated in the novel. Perhaps I'm reading into it too much, but given all the information I suppose it can be assumed that when Yuna came back to Besaid over the course of FFX2, she would avoid the temple, and by extension the elders. Hence, even if we don't see much of the elders throughout the games, it's not unlikely that they would occupy her and disallow her from interacting with Tidus.
Again, just my two cents on the controversies surrounding this entire novella-- a novel can be interpreted in so many ways, especially given how vague the Japanese language is. I'd like to believe Nojima didn't just up and decided to butcher the entire series just to create a bit more drama. I do appreciate the backstory he is fleshing out for us, although of course I haven't had a chance to read the rest of the novel yet, so... In any case, thanks so much for translating the novel once again!