Update: CT scan reveals heart is 100% clear, no QT delay etc. Next step is planning a sleep study. Note that I had the same symptoms (but not as scary) last night falling asleep, two times. So it's not just "in the head".

Elavil dose down 50% now without too many problems. I might still consider continuing a low dose (10-20 mg/night) given the possible link to nerve regeneration.