Hello,
I addressed the issues you mentioned on patch 0.1.1.
Eilayda's stats were boosted, and damage spells' mana consumption was slightly adjusted to make fights less difficult.
Now events in the dungeon should not be repeated when you use the stairs.
The latest game version (0.1.2) is available for download.
I recommend you start a new game, if you follow the update instructions, you can skip the prologue and give another try to the kidnappers’ dungeon with these new changes.