Those are good news, I'm glad you managed to sort it out for the time being. I'm fine with having the teutonic culture available only on Anno and the player, it reminds me of Prophesy of Pendor where certain companions have their own units regardless of the kingdom's culture chosen by the player, thus adding to the lore and immersion of the characters.
The reason it doesn't apply to every lord/lady in the kingdom can be further explained lore-wise as the player making an alliance or simply empowering this minor faction through the companion. This opens up roleplay options for the player as well since he can also access this culture and make it part of his background story, whether as a crusader bringing order with the teutonics, as a dark elf reclaiming the confederacy lands for his people or as an amazon raider establishing the amazons as a civilization.
Well you get the picture, even if it didn't turn out the way you originally wanted it still works in a good way.
About the village recruits not changing according to the player's culture I've noticed before but I guess I forgot to mention that previously, perhaps looking into a module system of a mod that has the town/castle recruitment script to compare it with yours.
Having all the cultures unlocked for selection sounds good as I sometimes helped a faction, was employed as a mercenary for them or simply had a mixed army but wanted to choose a different culture than the one's I had unlocked when founding my own kingdom.
To finish up, best of luck with your new internship/summer job.