Raids in Force - The Dahan are dealing the damage, as they are the ones carrying out the raids. Note that a land can have no Towns or Cities and still count. Meaning that suppose a land has, say, two Dahan and three Explorers. There are more Dahan than Towns or Cities in that land (two versus zero), so they will deal damage. So you would kill two of the Explorers.
Missionaries Arrive - Yes, treat all Cities as though they deal six damage instead of three during the next normal Ravage. A "normal" Ravage means the one that occurs as usual during the Invader phase, as opposed to one triggered by something else such as that Major Power that I've forgotten the name of (something-Manifestation, I think?) which depicts Lightning attacking an Invader settlement.