Well not to spoil too much:

1) Eilis isn't in a dark place.

2) They both may use 'old words in expression' but they themselves are the ones that pull and manipulate the Aether in accordance to their link with it. The words themselves are more words of focus and not necessarily spells, they are of the same language though.

3) I will however agree that it may seem mystical and powerful but remember Eilis's magic normally works as a conduit, she still is bound.
The soul is linked to the Aether, the body the battery and vessel.

4) No you didn't read it wrong, poor Tyr got blinded and stabbed. 

Spoiler hint: [url]https://www.youtube.com/watch?v=XFBNAj7P7Nw[/url]

Also I will write a proper reply tomorrow.