Is he showing signs of SA during the day as well?
Do you have a nightlight in his room?
Does he have a lovey?
I'm really surprised that he freaked like that....hmmm...
So, are you still lying down with him every night at bed time, and staying all night - or are you sleeping in your own bed coming back to the mattress only if/when necessary?
If you're sleeping in your own bed, and he's sleeping through the night just fine, you might just leave well enough alone for a while. Then, in a week or maybe longer...just pack up the air mattress one day when LO is not around to see you do it. If he asks, just tell him that it's put away. Then at night, stay with him till he falls asleep (or whatever you're doing) and more than likely, he'll sleep all night if he has been!
If you guys are still sleeping all night on the mattress, try ditching back to your own bed so that you can get yourself to the point where you're only going in if you have to.
Let me know!