I just did my first dry incubation and kept my humidity between 25 and 35% during incubation and upped it to 55-60% during hatch. I don't know how the humidity pump works, but all I did was keep two calibrated hygrometers in the incubator, ran it for a few days before setting my eggs to see where the humidity fell without any added water. Then I added a little water to see how high it jumped to gauge what I would have to do come lock down. Once I was satisfied, I set my eggs and only added about 1/8 cup worth of water into the smallest available well (less surface space so only a slight adjustment to humidity which is all that was needed at the time) to up humidity twice during incubation and then again for lock down (which I used all three wells to up the humidity where I needed it).
I only had one chick hatch out of 12, but I don't think it had to do with my humidity. I think it had to do with the removal of a fan that had been in the room as all the chicks that died did so during lock down when the fan had been removed.
I hope my rambling makes sense.
Edited to add: This was also for chicken eggs. I don't know how this all translates to duck or other eggs.
