1. Are the 7 incarnations of Haas all in his labyrinth? I think I've gone through every part, and I've only killed 5.
All of them are in the labyrinth. Some rooms look alike, so you may get confused. Get a pen and paper and write down where have you been
2. Is there an exit out of the labyrinth other than into Murock?
No. It goes from the Valley of 1000 rivers to Murock (and back) and that is it
Be careful in the end battle vs. Haas as well. A lot of melee troops seem to be in order.