I’m not a competitive player, so my suggestion comes from a casual/fun perspective, and is also more along the lines of “what could be” rather than “do it like this!”.
For Teutons, rather than throwing bigger numbers on units, why not make use of the “Teutonic flavour”?
Defensive (durable and long range), strong faith (monks+monastery), infantry focused.
Teutonic Knights have ties with religion. If they need to be faster, why not make use monastery tech?
Fervor affects Teutonic Knights.
…or maybe all infantry (but remove squires; else this would conflict with Celtic infantry bonus).
…or maybe Teutonic Knights and Paladins.
…or maybe Teutonic Knights and spearmen-line/trash units.
…or maybe, because of the Teutonic Order being tied to monasteries, why not have Teutonic Knights be similar to Huskarls+Missionaries (in classic version)?
Teutonic Knights can be created in monasteries…
…once you’ve build a castle.
…as long as you have 1 castle alive.
On infantry having more defense: Again, why not make ties to the monastery?
Barracks unit benefit from Sanctity (+15hp (= 50% of 30hp of monks), not +50% hp)
…or maybe it applies to all foot units.
…or maybe to all gold units (only non-siege).
…or maybe it applies +50%-hp bonus but only to spearman-line (or all trash-units).
Having higher hp (rather than defense) might even benefit the longer healing range of monks?
On giving barracks and stable units +1 armor: Why not make use of Ironclad, similarly to Yeomen affecting different things?
Ironclad: siege weapons, barracks units, stable units extra melee armor
Then you can have different values under the hood for the individual classes, for instance:
siege +4(?), barracks +2, stable +1…
Just some thoughts.