Why Does Auron Act as Though His Arm is in a Sling?

[Renmiri]

I suppose his faith in Yevon has something to do with it too, once he learnt the truth it destroyed his faith.

So out of curiousity... do we see him with his arm in a sling after we learn the truth about the Yevon church?

Yes, he learned it before he died, no ? He saw Braska die in vain and knows Jecht turned into Sin.