Marros

Canon Classes should probably be whatever class they level up into when you haven't recruited them, or what they show up as in the war phase.

That's Correct. Any crest item prevents a unit from being damaged for using relics, while using the matching crest lets them use that relic's combat art.

Classes affect your stats in two ways, Base stats and Class bonus. Base stats work like they do in Echoes, where changing into the class brings each stat up to the listed base if it's lower. (for example, changing to Gremory with less than 17 Mag will bring you up to 17, but does nothing if your Mag is already 18 or higher.) the class bonus is a modifier to your stats for as long as you are in that class. in your case, the warlock class bonus is +3 mag, +1 Dex, +1 Spd, and +4 Res versus the Gremory's +5 Mag, +2 Dex, +1 Spd and +4 Res. You can see the adjustments using the info button on the reclass/certification screens.

they don't change at all outside of the Lords switching classes. the first post-skip chapter was a hell of a thing for me since I had swapped out half my original class for recruits and they were way behind.

Same as any other Knights/Church members, just requires level. He's definitely got the lowest requirement out of them though.

You miss the rest of the month's instruction and free days, so hold off.

So if I'm reading you right, as long as I keep using the same file for each NG+, I can buy my skill levels up to the highest level I've ever had them at, regardless what playthrough that was in?

Unless I'm mistaken, it is actually "must have a crest", in that anyone with a crest can use the weapon, but only someone with the matching crest can use the associated Combat Art. I believe you can also do so with the Sword of the Creator, but it has 19 weight instead of 9 for everyone except Byleth

"why would anyone romance them" is a terrible blanket statement to make for the whole fandom. you might not want to but plenty of other people see some appeal in dating the fantasy pope. Also, implying that they have to get married for it to be a real romance is kinda iffy as well. It'd be nice from a representation standpoint to have two girls (or two guys) definitively stated to have gotten married, but you don't have to be married for it to be a romantic relationship.

Raises MT when using a weapon.

I've been hit by so many sub-35% gambits at this point I'd buy them having gone back to 1RN.

Those Max stats are absolutely absurd... can you even reach them?

Well, looking at the character spell lists, I now see why Dark bishop still has Miasma Delta as a class skill instead of just doubling uses of dark magic. Because there is one playable character in the entire game that both learns any dark magic naturally and can actually use the class (Hubert). The choices on this class confuse me greatly when there's only three characters who learn dark magic at all and two of them are girls (Edelgard and Lythisea).

IIRC, Vantage was only for Hero. Swordmasters get Sword Crit +10 instead.