"1. With the ZLD, if I turn the tower control down how is that affecting the amp? Voltage? Wattage? or is it just lowering the volume post amp? (i am no electrician.. ) My concern is i dont want the Harpoon running wide open with the tower vol turned down...i'd want the harpoon running lighter..."

Think of an amplifier as a water valve. You have all this voltage potential from the battery system backed up by some serious current (force). Just like a giant water reservoir.
Then you have the output that goes to the speaker. Just like the garden hose output.
The input from your source unit or EQ is like your hand on the water valve. It opens and closes thereby restricting or opening the pathway from the supply to the speakers. You can have a light stream or powerful stream. And of course the supply is also modulated (pulsing so to speak) by the dynamic music.
If the amplifier valve is nearly closed by the the source unit or EQ then very little of that supply potential is flowing and the inverse is true if the source unit or EQ substantially opens the amplifier valve.
An amplifier is a unique electrical multiplier in the sense that you can control this gigantic reservior of potential (battery & charging system) with the very tiny audio signal from the source.
Hopefully I have helped take the mystery out of controlling the amplifier.
The amplifier doesn't really generate power as much as it just transforms the available supply of power. When it is turned down it simply does not pass power.
There will always be a certain amount of idle current when the amplifier level is reduced. But it is not enough to be concerned with.

David