I on air con, the RH is still around 50%, actually then is the correct recommended healthy level.
However, if the air con is placed directly infront of the bed, the air blows straight to your face while you rest, then that's a problem and yes that aggravates throat irritation.
I will spend the money to shift the air con to another location or try tilting the air con's vent away. Humidifier, is still not a wise idea. Humidifying, will only make you feel hotter and cause other issues, even if the temperature shows lower. As you can't perspire properly to cool yourself, due to the high density of water in the air.
I ever tried at RH40%, temperature at 31 degrees.
I dont feel uncomfy at all. No sweat.
Lower to 30% rh, 28 degrees feel pretty cold.
It's the humidity more than the temperature that makes you feel hot and stuffy.
Dehumidifiers can be purchased from TB at i think $100+.
Should be the same for humidifier too if you really need it.
Dehumidifiers need to drain out water. ( I had one full tank of 1 litre in around 3 hrs iirc.
Humidifiers need to top up water.