No problem. Good luck and let us know how it goes! :)
Yes, you can try to make a tiny safety hole near where you see their bills in the air cells to be safe. Look very closely at each egg when you take them out to do this, to be sure there are no tiny external pips that you couldn't see from outside the incubator. If there is any little tiny crack in the shell, it is externally pipped and can get air and does not need any help making a hole. Be very careful, all they need is a tiny hole through the shell and membranes of the egg in order to get air. You don't want to risk nicking a blood vessel in the inner membrane.
Have the incubator open for as little time as possible as you take out and quickly return each egg. Mist the eggs and inside of the incubator with lukewarm water when you put the eggs back in so you can get the humidity back up asap.
Exactly. ;) It's not really that important to make the little safety hole in precisely the right place where they will start to break out. So long as it's in the air cell it will get them the air they need.
And don't panic, ok? This is just a simple safety procedure so you don't have to worry about them taking a little longer to finish hatching out. So long as they have air, they can take their time hatching out the rest of the way. Ducklings will not hatch out until they are ready.
It is Day 26 for them now, right? They are still ok! This is just the average Call duck hatch day, but sometimes they can take a couple more days. Incubation times are always give or take a couple days, for any species.