Regarding Garlemald...
All of this is completely irrelevant right now. None of us know any of these things about their lands or their past, in-game; we just know that war with Garlemald is looming, and they haven't been especially open to bilateral negotiation in the past. Does the Eorzean Alliance even have communication channels with Ala Mhigo?
(I do agree that the Garlean Roe was more than a little bit cartoonish, and as much as I love me a good solo instance, I wish that sequence had been used to better effect. Maybe even as a way to introduce Zenos. I dunno. It's definitely my least favorite thing about the patch.
As for that checklist...well, Cilia covered most of what I wanted to say, but a couple other points:
Plus, Crystal Tower was where he showed that he could be relied on in spite of himself, given the right circumstances. It's the only reason we "trust" him at all, to the point where I'm kinda curious how that scene plays out if the player hasn't done CT. Hell, we're even given the chance to Not Trust him ourselves, in those opinion options you disliked so much. Also...
I mean, he's a pretty sneaky dude. That, and the average Gridanian likely hasn't seen a Garlean outside their fully-armored conscripts and soldiers - the eye may not register at a quick glance, if they even got that. I could see nobody paying him too much mind until he ended up somewhere he wasn't supposed to be.
In addition, we haven't been given the narrative thrust to do so, for the time being. This game has played with storytelling in an MMO environment since the start; this time, it would seem that they decided to provide us with a reason to move East once we could actually do so, rather than end with an explosion of urgency and then expect us to lollygag around our old stomping grounds for three months. Clearly, it's gotten mixed reception, but I can see why they did it. We'll get our reason for going to Othard in 4.0.