About the teleporters: There is a lever in the far NE room which should be activated to proceed further.
About the deadends: I think that should be Josephine's one. Do as maryjo suggested. I also had some difficulty finding the door in NE corner. Just click to other room to see if there is a way to go there. If there is, your character goes automaticly.
I also suggest you to look to
this topic for maps of those fortresses.
