I've open mine a couple times but the humidity stays the same. I also mist when I do open. I opened once to remove two chicks that were reaking havoc. They'd been in there about 36 hrs. Once more to remove a batch that where on day 28 and never hatched .
I say help it hatch, s-l-o-w-l-y. take a bit of the shell off and see if it can break through the membrane. If not, just make a small slit (it doesn't take much really) and see it that helps. I helped two of mine 2 wks ago, my first time hatching, and they are thriving. They would have died otherwise. I ended up taking a good amount of shell off the 2nd one but made it work as well. Just keep an eye on it and do what is needed.