Don’t worry about using all the eggs, if you have achieved the consistency with just 4 eggs, you are good to go. If you needed a little more egg, always use the yolk first before the white. If you need more, add in another egg. It all depends on the cooking evaporation process, the accuracy of the cup measurement and the size of the egg.
You can pipe the choux paste onto the sheet pan and freeze it. Transfer the freezed choux paste into freezer bags, squeeze out all the air and zip lock tight. They can be freeze for up to a month.