No, it was you saying the filter was on the floor that got me.
Get the filter as high and close to the exhaust fan as possible. All that vent tube is slowing airflow, and all your heat is staying up top. You're venting the lower cool air and keeping the upper hot.
Your passive intake into the room should be low. The filter in the room should be high, and connected as close to directly to the ventilation fan as you can manage, which shold also be high.
But yeah, humidity will shorten the life of your carbon.
Oh, and nice setup BTW. Mine is so ghetto, hahaha.