If I understand your original post, your filler neck breather is open like this picture from the CJ3B page, right?
You mention you don't have the original air filter (I'm guessing it was an oil bath for a '56 correct?)
If that's the case then your problem isn't just humidity, it's that you've defeated part of your Crankcase Ventilation system and this is causing excess humidity to form in your filler neck. Depending on your top valve cover (may or may not have a vent port) type,
(possible valve cover configuration from CJ3B page)
that port and the open port on your breather neck should tie together and be connected to your breather.
Image from CJ3B page showing diagram from service manual without tie-in to valve cover ventilation hose.
If you've swapped your air filter breather to a different type, there should already be either a port to attach a hose to or look at the adaptor (whether metal or rubber) that connects to the breather horn on the carb to see if that can be adapted to accept an attachment for a ventilation hose.
If this is done, your condensation problem should resolve itself. That port should not be plugged shut nor left open.