+1
This quest is quite a mess, gameplay-wise.
At the very least, the game should automatically put you in turn based mode when the door opens, in the same way as it does for traps that require time-sensitive action to escape (eg the trapped tomb in the ruins).
Agree. This could help a bit (that and fixing NPCs not moving to their next spot).
Side note : especially when the "Turn based mode" is not the most inviting feature to be triggered manually. Personally, I find that feature a bit rough, mostly because it takes a long while to activate and deactivate.