I highly recommend reading hatching 101. It's not perfect but it has a lot of great links. I read through it 3 times and read every link before my first hatch. It will equip you with everything you need to know to get started.
https://www.backyardchickens.com/a/hatching-eggs-101
And Amy's link for humidity is the best!
I recommend this article to everyone with humidity issues. So many people with failed hatches are asking why on the threads. When you get their basic hatch info they say they did this, that and ran 50-60% humidity and have no idea how that correlates with the air cell on the egg. That's when I copy & paste the link to your article!
I also use sav-a-chic for the first few days with every hatch. If you have a chick with issues then you can give a drop or 2 of the nutridrench. With ducks I skip the sav-a-chick and go right to the nutridrench. You said your one chick has splayed legs? How old is the chick now? I know with my bantams many of them appear to have the splayed leg look but after the first 24 hours they are running around looking good. If it is true splayed legs I really like the vet tape. If you can't get "vet tape" Walmart sells an "ouchless tape" and it works the same. Cut a thin strip and make sure the chicks legs are wide enough for it to walk but tight enough to correct the splay. It's flexible, holds up good and is super easy to take off. Good luck to your little chick!! 
		
		
	
	
 that's awesome!