Just a short note (I'm german so my english might be strange...):
I would change the Fighter's Armor Training so that it also improves the max. Dex of the Armor worn.
Either in substitution for the reduced ACP or in addition to it.
I think this might be more appropriate because the ACP has something to do with the "bulkyness" of the armor getting in the way with certain activities
and the Max. DEX is more like the weigth which slows a character down.
So a Fighter used to wear armor might not ignore the bulkiness of his armor but gets used to its weight and thus isn't as slow as without training.