This doesn't sound like night terrors, just lightly recurring nightmares. Actually, come to think of it, this sounds like PTSD. Perhaps he can talk to a therapist? If this is trauma based (and trauma can be something seemingly trivial and harmless to the common eye) talking with a therapist and getting to the heart of the matter might be what it takes to get through the nightmares.

For during the nightmares, talk to him while he's there. Physical contact (gentle, non-waking type), and reassuring words can ease him through the nightmare. I've used this with my 4 yr old AND my wife (MandaMay) before.