Statistics are so interesting precisely because they are so difficult to interpret.
Based on your descriptions, I am guessing that none of the words G-d, Jesus, or Christ, was used in its religious context but rather as either an expression of fear (Oh, my G-d!) or as profanity. Therefore, one interesting correlation would be the rate of all swearing in expression of fear or profanity. If the rates have similar decline, then you are just seeing a correlation between profane words and the movie gross. There is still a lot of work to be done if you make that correlation, but that's where I'd start.
Shalom.
Still crap