Don't let the membrane dry out, please. It's important to keep it damp until the duckling is ready to complete the hatch. What happened so far in the hatch was perfectly normal. Duckling hatches can take up to 4 days to complete from start to finish, though most of them complete the process in 2-3 days. First they pip internally, into the air cell inside the egg. It could take up to 24 hours before they progress to the next step, external pip, when they pip through the shell. Once they've done that they will rest again. During this rest period they will finish absorbing the yolk sac and the blood vessels in the membrane will slowly recede. This process can take another 24 hours, sometimes longer. During this time the humidity in the incubator should stay high enough (65%+) to stop the inner membrane (the membrane covering the chick) from drying out and shrink wrapping the duckling. A shrink wrapped duckling could easily get trapped by the membrane, unable to move in the shell and position itself to zip the shell open and complete the hatch.
It is important now that you keep the membrane damp and keep the little one in the shell until it's ready to come out. As long as there are still visible (active) blood vessels, it needs to stay put. How much of the shell have you removed? Would it be possible for you to post a pic of it?
