They are going to be weak and need some rest. Most of the time they can survive a few days on the nutrition they got from the yolk sac. It you want you can put out some water and scatter a tiny bit of food on the floor. I would suggest going ahead and giving him some poly v sol vitamin (without...
I am not an expert by all means....however:
1. The duck should be safe.
I hope you have a heat lamp over him and are watching the temperature? You can place a damp sponge in the box to help with the moisture in the air. You can also quickly put a fine mist of water on the egg to help from drying...