The upside down cross is meant to be the satanic symbol in the show. When in reality the upside down crucifix isn't satanic at all, it is the st Simon Peter cross which he requested during his martyrdom in 69 a.d . He was crucified in this manner because he felt he wasn't worthy of being crucified in the same manner as Jesus Christ.
Andrew Rothenberg plays a character named Jim, and is best known as another Jim from season one of The Walking Dead.