What do you mean by "...moisture creeping down the walls..."?

I really don't see how you can have "too many returns". Most people could use more. One in each room would be ideal, but is expensive so not often done anymore.. I am in your area. A couple of years ago I got estimates for re-doing a 2000 sq ft home with good equipment and all new ducts. The costs were $12-13k. If you are getting new ducts then 15k would not seem unreasonable. 3200 is a lot of house.

If your ducts are outside of your house envelope, your moisture problems very likely come due to pressure differentials induced by the AC system. By outside, I mean in the vented attic or crawlspace. What happens is that leaky supply ducts blow air out and at the same time, in other places, moist air is drawn in to replace it. Either that or leaky returns suck air in and it has to be blown out through leaks elsewhere. The wet closets might be near the places where air is being sucked in and hitting cool surfaces causing condensation. Air often leaks in around poorly sealed "vents" and causes condensation too. Your closed-off ducts could have aggravated that problem. Note that "no leaks" might be a relative thing. The investigator might not have found any big leaks, but a typical residential HVAC duct system that age might be losing 20% of its air. Note that the insulation that you have might be great, but that does not speak to air sealing. You can have great insulation and still have a leaky house. Both duct and house envelope leakage can be determined by a blower door test.

Another thing that causes high humidity is a system that has more cooling capacity than needed, They short-cycle rather than giving good, long runs that lower humidity better. At this time of year, you are in a period where demand for cooling is low and humidity becomes more of a challenge for even a right-sized system. As a stop-gap measure, you should consider buying one or two portable dehumidifiers. It is also important to monitor your relative humidity levels. Buy two or three electronic thermometer/hygrometers. Check them against each other for accuracy. Your humidity levels should be below 50%. (They should also be above 30%, but I think that you will rarely have to worry about that!) If you can lower your humidity with portable dehumidifiers, you won't save any electricity but you may be more comfortable at a higher temperature setting.

Thank you for the response. Well moisture creeping down the walls in both closets are what appear to be moisture spots and green spots of possibly mildew? I have sprayed them with tea tree oil as I read this will kill the mildew/mold. The first tech that came out told me the humidity in my master bedroom is 70%. Crazy huh? Cardboard is working to drop it in the bedroom returns I can tell, air is much less humid. I will look into portable humidifiers, but hoping to find another solution that will work and is in my price range. Where can I buy the thermometer/hygrometers please?

You want a DEhumidifier. Something like this should work for hygrometers:

La Crosse Technology WT-137U Digital Thermometer/Hygrometer with Comfort Meter

I think that you should remove the wet drywall in the closet. You can easily patch it there yourself. It does not have to look pretty so anyone can do it.

Ask the HVAC companies that looked at your system if they can slow down your blower or look at the model numbers and post them. The pros here might be able to say if it can be slowed down and how.

that 500 sq ft per ton of ac is eating your lunch.
$600 utility bill...that is crazy.

when units are grossly oversized they don't run
long enough to remove humidity.
this time of year as it gets cooler the units
run even less.
RH inside house rises.

I'm not suprised at 70% RH in master bedroom with
bedroom bath & maybe 2/3 closets & 2 ton unit.

see if unit's dip switch settings can be lowered.
Ultra air makes a great whole house dehumidifier
which would help with lowering RH year round.

entergy has a program with energy raters in N.O.
perhaps it is something you can take advantage of?

you can by Hygrometer's at wal mart, kmart & even
radio shack. I have the type with multiple channels
so that I can monitor outdoor temps & RH, indoor
temps & RH in several locations in my house.
knowing what RH% your house is holding
is good info.

mold needs two things to live. moisture source
and food source. address the moisture source
clean off the mold & it will not reactivate.
but you have to stop the moisture source first.

best of luck.

Thank you both for the replies. I will buy a Hygrometer, and yes, I think that before I can even address the mildew/mold I need to stop the moisture. Going to call and see about whole home dehumidifier to add on to my hvac, the cost seem much easier to deal with too and I am hoping it will alleviate the humidity. Thanks again!