Don't do a float test! That's a good way to kill potential chicks. If you're not hearing anything and you don't see any movement when you candle, they're probably dead.
There isn't a way that I know of. Some crooked neck birds survive, some don't. I had one survive until I culled it at 8 weeks, another one seemed to be doing okay until it just started to fail at about 4 weeks.
72% is waaaay too high. I keep mine at about 30% during incubation and raise it to 50-60% at first pip. My first couple of hatches I had the high humidity and ended up with several curled toe chicks. I've had very few since I started using lower humidity.
Too long in the egg can also cause...
Ouch. Sounds like your humidity was high during incubation. You can try the cup method where you put the chick in a cup that forces it to stand upright. They might improve, but be prepared to cull if they don't.