Yes. The region is then locked, and Nightmare dies. Locking the region is triggered on these conditions: Callo dominates a region where there are two nightmare tokens, and the Faun is present. If these conditions are met, the region is automatically locked. 

No!
Fiolsfinn must dominate region to use this special ability.

Yes. 

Yes.

Yes. Influence markers disabled by Vuko are still in the region, so the Ice Drakkar may take them to the Ice Garden. Faun may exchange influence markers under Vuko`s control as well.

If an initaitive marker passes over a scoring symbol, it always triggers region scoring at the end of that turn. So there will be a double scoring in this case, once for passing over the first scoring symbol, and a second time, in immediate succession, for the second symbol.