So sorry, it must be so difficult and I assume it takes time to calm them with night terrors. You need some help, can your DP take over to let you sleep or can you get some respite? You will struggle to cope if this goes on and it would be a pity if the placement were to break down.
My LOs are really bad sleepers and I am on my knees with fatigue. Been with us 3 months, oldest had nightmares, youngest (2.5) still has bottle at night and wakes constantly, thus waking the oldest or triggering more nightmares. Youngest also having night terrors.
(Bottle is essential as he was not really weaned when he arrived and will not drink in the day (unless bottle) - so we have stopped daytime bottles and gettng him to drink from straw, but making slow progress. Nighttime bottle is as much about hydration as comfort/food.)
I am, on average, up 4 times a night with them. Last night was 7 times. I am cream crackered and its affecting my ability to parent effectively.