You may be right about Sophie killing Brother Justin. She seems to be wising up to him in the most recent ep, and she does like Ben. But, she may just play a crucial part in helping Ben kill Justin, as I predicted a while back. Also, I am becoming more and more convinced that Iris really does plan to turn against Justin, as she seemed to know what Ben was up to, told him where to find Justin, and left the axe on Justin's pillow. I predicted her turning too, when others thought it was impossible. But, then I thought I understood her motive. Now, I realize I don't know it at all.
Psion Ten, it does seem certain that Ben and Justin will meet in the final ep of the season, but I am far less convinced than you that this will be the last season. Still, I don't know how they would extend things for another full season. I guess we'll just have to wait and see.