I admit, humidity is hard to control, especially since many people (and manuals) state different humidity levels). 60-70% though is more what you want for hatching period, not the incubation period. Incubating is a learning process so even if you don't get a good turnout with this batch, keep trying. Eventually you'll get it so it works for you without problems. Only thing to bear in mind is avoid opening your incubator the last few days (and stop turning if you turn manually) because the chicks are readying themselves into the correct position for hatching. When your chicks hatch, leave them in there until you believe all have hatched and they are dry otherwise they can get chilled. Chicks are fine without food and water for about 24 hours after hatching.