carestx - I think I have figured out at least one of your concerns regarding humidity. You report that when the system runs the humidity goes up, not down. I think you mean to say the "relative" humidity goes up.
Humidity is the amount of water in the air. Relative humidity is the % of water in the air relative to how much it is capable of holding.
So by lowering the temp it changes the ratio and % of water in the air at that temp.
Warm air can hold more moisture than cold air. Think of the heat in your house at 78°F as a big gulp cup. Then think of the heat in your house at 68°F as a coffee cup. Fill the coffee cup with water which represents the moisture in your air. The coffee cup is 100% full or in other words you have 100% realtive humidity. Then pour the water from the coffee cup into the big gulp cup. You have the same amount of water but now the cup is only 20% full or 20% relative humidity. So in this way a warmer house can show a lower percentage. Warming the air is like having a bigger cup because warm air can hold more moisture than cold air.
All this still doesn't forgive the fact that you are uncomfortable. What you need is a removal of moisture without a lowering of temperature. When your humidistats call for reducing moisture the blower in the furnace should slow down and make the coil sweat more. If this isn't happening then we should probably start there to figure out why not.
Looking at the pictures I am very concerned about what happens in worst case scenerio when only one zone is calling. Where is the extra air bypassed? I would like to see a pressure reading in the supply plenum with the smallest zone calling for cooling. Those VS motors can only stand .5 max static pressure and you sure don't want to be replacing those babies every year.
Another concern is accessability. Can a man stand in front of those double stacked monstors and reach the upper unit to effectively work on it? When there is that much head room it works out much better to stand the furnace(s) upright.
"And remember my sentimental friend......that a heart is not judged by how much you love, but by how much you are loved by others" - Wizard of Oz.