I either do this or close the vent (make sure to open it again after!) and just open the incubator enough to side a hand in to sneak out an egg then close it again. It will drop down in temp and humidity but will jump back up fairly quick after you are done. I find having the vent closed while I candle will help with temp and humidity while I am candling at least a bit.
I also got a magicfly candler on amazon (thanks
@Iluveggers) but I have used the incubator one. you can try to use your hand to block out some of the light and that will help. Some eggs I am hatching are brown and while not super dark they must have thicker shells since they are hard to see in. day 3-7 was harder to see so i wait. around day 10-14 you will see more of the dark shadow and see it moving around which makes it easier.
You should smell something well before anything explodes. I have left some in there for most of the hatch as a ? and haven't had an issue with any exploding, or smelling actually. Just smell them to be sure they don't stink like a rotten egg, if they don't they are good to go for longer.