I would suggest contacting the pastor since he left his number. Maybe if you call and explain why you are parking there and find out if it okay during non-service hours he will let you. A donation would be nice since they do have to maintain their lot.

Is there a school on your route? Most of the schools here do not mind people using their lots for parking on weekends, especially now that it is summer.

For commuting DH and I park at a large grocery store. So far there has not been an issue, but we park in the back of the lot where customers do not park. The employees park back there but they still have plenty of open slots.