Fantastic job. You didn't railroad the players, and allowed the roleplaying and tension to play out, and also provided some interesting plot developments for future sessions. Great job!
By the way, as far as the cleric's curse is concerned. how about this:
Take an evil warlock spell that is of a higher spell level than the cleric can usually cast, and whenever the cleric uses it to slay a creature, its soul is sacrificed to the dark power from the weapon. The more she does it, the stronger the big bad gets. And then of course tempt her to use it.