That's very interesting. Sounds like he's stronger than he looks. Let's just hope his organs are normal. If they are, I'm sure he'll learn how to navigate his legs. I would keep a watchful eye on him with any other chicks. His bum legs look just like little worms. Keep us posted on your little guy's (or girl's) journey.
I had one of these hatch out last season. The bird lasted about three days and wasn't able to move around well enough to eat, drink, etc. without assistance. (And even then, the bird simply got too weak.) I hope your bird does better than mine did.