You mean the windows are not supposed to be wet inside all the time
JK I am having sweaty window issues also, I am almost certain it has nothing to do with the 350 gallons of salt water and the 4 gallons a day evaporation, I am blaming it on the toilets as the tanks sweat when you flush
I am thinking HRV is the way to go, especially as the furnace is located in the same room as the tank.