Will a dehumidifier help?

dehumidifier yes. take damp towels out of bathroom daily, leave door open. a floor fan blowing air into the room will also help more than the crappy fan. or replace the fan. wipe areas with diluted bleach. appliances now come with a rating, while includes an estimate of monthly cost of operation. see if you can find energy efficient humidifiers and I bet your AC costs will come down. Humidity is the most challenging element for ACs.