Oh god, that's terrible! My thoughts and prayers go out to Mark and Baize's family.

Right analog stick should toggle your targets.

Non-rhetorical question: How do I do that? Is it the “break” message that appears when I hit especially hard randomly, or do I trigger it more by facing my character towards a tail or horn or something before I swing?
It involves focusing your attacks on a certain area of an enemy. You should be able to cycle through what part of the enemy you're locked onto to make that easier.

Non-rhetorical question: there’s a blue bar on the bottom of my screen that gradually runs out. Does that impact how fast I run? Do my stats in combat go down when it empties? What does it mean?
There's a glare, so I'm not completely sure what bar you're talking about, but you mean the one in the middle that has icons over it?

That bar keeps track of how long the buffs from the food you ate last.

The movie’s most famous song, “When I See an Elephant Fly,” is sung by a chorus of African-American-voiced crows, led by one literally named “Jim Crow.
Jim's voice actor, Cliff Edwards, wasn't even African-American. He was a white guy.

It leans hard into a particular brand of fan service that puts me off personally.
Yeah, as I recall, that was pretty much the reaction of a lot of people when Cindy was first revealed. Director Hajime Tabata's defense was that she wasn't meant to be seen as erotic, just "very energetic and outgoing". He didn't want to change her design concept after getting that feedback, but figured if they moderated the way she's presented then it'd be fine. Apparently there was originally a lot more breast jiggling physics with her.

To me it just sounds a lot like the response MGS V's developers gave where they defended the design of the character Quiet as "it's for story reasons not fanservice". There would've been ways to probably still get across Cindy's personality with a less revealing costume.

Art by spacefeels

Even just some minor touches like zipping up her top so her bra isn't showing and not making her thong visible would've been better.

Also, in Japan her name is Cidney, making the connection to Cid even more obvious. Originally people thought she'd be THE Cid of the game before her grandfather was revealed. So instead she's more like Mid from Final Fantasy V, a grandchild of Cid with a similar name.

Non-rhetorical question: this game feels intensely American at times so far. Is that intentional, or do Cid and Cindy and Hammerhead also fit Japanese archetypes I’m unfamiliar with?
I think it's more deliberately designed to invoke the feel of the southwest US, particularly the environment. While there are sand dunes in Japan, it's not quite as iconic nor seen in media nearly as much. Road trip on the desert road make me think of movies like Fear and Loathing in Las Vegas and such.

Non-rhetorical question: does this mean they do increased damage against flying/floating enemies?
More like they're capable of being used in mid-air and offer better mobility against flying enemies.

Non-rhetorical question: is this the advantage of a primary weapon set over a secondary? Can you only do techniques with your primary set?
Nah. At most, I think some abilities that use the primary weapons can be learned before the secondary weapons. Otherwise, it's probably more that the AI is just more likely to use the primary weapon.

Oh, and his city is Insomnia. What a crap name lol – who’d want to live there?
Well there's New York City, whose nickname is "The City That Never Sleeps", which is similar in meaning to what insomnia does to you.

I know before starting that FFXV has a ton of tie-ins outside the main game.
You know, some people say series like Kingdom Hearts are hard to follow, but at the very least you don't have to stop playing in the middle of one game to check out something else.

If anyone has a (spoiler-free please) suggestion thing to add on, let me know!
There is a novel that should be done after everything else, Final Fantasy XV The Dawn of the Future. However, while it's been released in Japan, an English version won't be coming out until June 23rd, 2020.

I’m still hoping for a return to the slow, strategic pace of FFX
That reminds me, another FF spin-off that you could check out after FF XV is World of Final Fantasy. It had some of that slower, strategic pacing.

Non-rhetorical question: are the later-numbered main story chapters still considered tougher than the earlier-numbered main story chapters?
I think they might be roughly be around the same difficulty? Though that's only at the start. With the exception of Caius, all the main quest bosses get stronger at later dates. Noel gets stronger by day 7 (and wears his Battle Attire DLC costume from XIII-2), Grendel is replaced by Parandus on day 7 (similar looking monster and same battle style, just more aggressive and higher stats), and Snow has two stronger forms, one replacing him from days 6 to 9, the other replacing him from day 10 onwards (and his Cie'th transformation gets worse. He also loses his shirt by the last form).

A bit of foreshadowing that Lumina was a part of Lightning, Lumina is the plural form of lumen, which is Latin for "light". Lightning's name is sometimes shortened to Light, and her real name, Claire, is French for light.

Also, if you look closely, the surface of the new world that was made seems to resemble Earth. The place in the after credits scene with Lightning seems to be modeled after the French countryside.

There's also A King's Tale: Final Fantasy XV. Not really necessary, it's just a short game (the story mode is beatable in just 1-2 hours) that you could probably play at any time. I don't think it even really spoils that much if you play it first. Plus it's free to download.