T.H.
My youngest son at about the same age 2/12-3 years old had what the dr called Night Terrors, Where he would start screaming in his sleep his eyes wide open but he really was not awake. What we found to help him and us is if we touched him to let him know we were there, rub his back like you do and when he had calmed down we told him it was time to get ready for bed and we would get up and go to the bathroom, potty and brush teeth. It seemed to be the brushing of the teeth that indicated to him all was well. He would go back to bed and be asleep as soon as his little head hit the pillow. After a while it was simply getting up and going potty was enough. Perhaps it was just the fact he got OUT of bed and walked somewhere else he was really awake and not somewhere inbetween sleep and terror.
Good luck.