I know nothing about duck eggs.

WAY back when I was a kid, my sister and I were in 4-H, and we had some show chickens and we'd incubate the eggs. My memory is not super clear and it might not apply to ducks, but here is what I remember.

We were very careful with temp and with keeping enough humidity. IF I recall correctly, one of the problems with not enough humidity was that the eggs got harder for the chicks to peck their way out. "Very careful" is somewhat relative. We did measure the temp, but it wasn't digital. We didn't measure the humidity, just kept the section built into the incubator for water full at all times.

As soon as a chick started hatching, we would help it by pulling away some of the pieces of shell. This might have been because they were tiny little bantams, so they weren't very strong. I do not remember if we would do anything to cut a hole in an egg that was due to hatch but did not start pipping out by itself.

I know most of the other people we knew who were raising show chickens pretty much did the same thing with helping them hatch. I know some of those people also had ducks, but I can't say if they treated the duck eggs the same way.

Hope this helps.