I'm sure the back surgery is definitely related to his car accident years ago. Trauma often times comes into play many years after, especially in the back. If you watched Dancing with the Stars a few years back, Jennifer Grey was experiencing neck and back issues because of the same accident. Not to mention the emotional trauma that probably never goes away.
The only review of a show that matters is your own.
I can't see him having that big of a problem with his back... the role is definitely physical, and he's shown no signs of PAIN. Back pain is the worst pain, because it affects almost everything you do. He tumbles in this show... I think he's fine. Either that, or he's a better actor than we think.