hi R.--
we are just starting to go through this with our 4yo daughter. our son, who is now 6, had them for about a year around the time he was 2-3 yo and he grew out of them. with him, we would give him chamomile or sleepytime tea about an hour before bedtime, and then wake up him about 15 minutes before we anticipated the night terrors starting. we had moderate success with this--i think the precipitating factor was the birth of his sister. he grew out of it around the time our daughter turned 1 and he turned 3.
our daughter just began going through this a few months ago. the thing that seems to trigger hers is going to bed late, or generally having her sleep schedule thrown off. we just got back from a week's vacation about 10 days ago and both kids pretty much stayed up as late as they wanted to while we were away. the result after we got back home was an increase in night terrors. she is clearly not awake or aware of what is happening. she can't focus her eyes and can't answer questions or respond in any way to what is being said to her. she is usually screaming for me, not daddy, but does not recognize me at all. last week she hit me in the face and said "let go of me! you're not my mommy!" soon after that she went right back to sleep and slept the rest of the night without incident, and in the morning she had absolutely no memory of what had happened. she thought it was a joke i was playing on her and kept laughing and saying that was so silly.
we just had one about 2 hours ago and all she would say was "ouchie! ouchie!" but could not identify what was hurting. she accepted a cup of water, after which she went back to sleep.
i think you just have to be super patient with this and understand that it will eventually pass. i think it's great that you have tried aromatherapy for your son--can't hurt and it might help. have you tried massaging him before bed? he may sleep better, and more soundly. the tea generally helps both of our kids sleep better, so you might try that. make sure he goes potty before bed, too.
hope that helps--good luck and keep us posted on how you guys are doing!