There was another thread on NAT not to long ago, and the suggestion was made to turn it into insurance.  I questioned it in that case, but I was told that was the correct thing to do.

Here, in this case, I would suggest that you turn it into your insurance company. First.  That is what you carry insurance for.  If your insurance company thinks they need to go after the church's insurance carrier, let them do it.

Then, it might be a good idea to sit down with someone from that church - whether it be the pastor, or the board, or ??? - and help them to understand how their actions hurt your farm.  If you want to contact the state fire marshall, as others have suggested, that would be okay also.  But I would start with your insurance company, regarding your losses.