^ I absolutely loved Bane's voice right from the get-go. It really made the character, and I had no trouble understanding anything he said, nor did the voice sound odd or disembodied in any way to me. It sounded like he was talking though something over his mouth, which he was.
No, real, explanation is given as to why Wayne's body is in such poor shape at the beginning of this movie. Sure he took a beating in the months to year he was Batman...
That's pretty much it. You answered your own question.