Sounds like your Amazon Sword has an established root system and is thriving. You could probobly cut back 75% or more, as mentioned and it will grow back strong. I generally pinch older growth off my Swords using my finger nails once or twice a month, to keep them from dominating the tank.
As for getting your Swords to reproduce. I honestly don't know. I've noticed my various Swords that are only 4-6" tall reproduce at a great rate. Where as my very large, established 16" with 30+ leaves never reproduce. (All of this is dependant on tank size, growth space, ligthing, nutrients etc.....).
Perhaps the larger dominating plants have a well anchored root system for gulping up nutrients, and are taller were they get the better light? Were as, smaller plants need to reproduce more in hopes of competing for nutrients and light, thus surving in nature.
Again, these are just my observations. This is a good topic. If anyone has any knowledge, it would be great to hear.