So the church in episodes 7 and 8 is significant because its where Jane had the funeral ceremony before laying his wife and child to rest. Going there is probably part of Jane's 'acceptance' of events and most likely Red John recognizes Jane's presence in the church as a sign of defeat.

One more observation, with the exception of the sheriff all of Blake Association members and Jane survived the blast while the Visualize guys got vaporized. Tis leads me to believe the bomb was under the couch and when Jane had the Blake Assn. guys move to the other side of the room, it provided enough distance to survive the blast. Soooooo, I think it is entirely possible that the sheriff also survived the blast and maybe packed some blood samples with the bomb to leave behind a vapor of his DNA when the bomb goes off.

If I was Red John and knew that a bomb was going to explode, I would hide behind the other Blake Assn. guys and use them as a human shield. Te bomb was high powered, but small enough to carry inside on your person, so if Red John put enough distance between himself and the bomb, it would probably be survivable. Talk about theatrics!