I've never checked the humidity inside the incubator but I try to keep the room at about 40-45%. At lockdown I will add water to the long tray in a tabletop Styrofoam and then plug the vent holes on top. With the Sportsman I run water in it constantly because the fan is constantly on. Been doing dry hatches in the tabletops for probably 15 or so years and have had great luck with it. The main secret is to candle the eggs before setting them and to discard ones with a porous shell, Cracked shells can be fixed with a wax pencil or crayon if you don't have many eggs from those birds to set.
Another thing that I do is to store eggs in the fridge until I get ready to put them in. I just warm them to room temp before putting them in the heated incubator and I won't check temps on the bator till the next day and then make my final adjustments if needed. As long as the eggs don't freeze they will be fine in the fridge, ours is set to about 43F.
Whenever you candle eggs move them around in a tabletop, if you don't the ones under the heating element will hatch first, I usually candle every other day, this helps to mimic the "cool down" period when the hen is off the nest to eat. .
