Run your humidity in the 30’s. During lock down you can bring it up to 50. Once an egg hatches it will spike. So no need to spike it yourself. The humidity fluctuations are fine.
#1 verifying that your incubator instruments are accurate is crucial. If they are not correct just adjust accordingly. Personally if you want Silkie eggs get silkie eggs. If your equipment is right on you will be fine. Kinda hard to mess up.