I can't make something out of those large pics. I mean just a simple diagram made from MS paint or a screenshot of your layout view in C2 would help explain what happens in your game (aside from what you have explained so far) since you said the sensors did not worked out so well. I don't know how you did it specifically.
Aside from sensors, you can also check your distance (between player and enemies) as another condition for enemy AI.
You might also want to use instance variables to store the direction an enemy is currently facing. So an enemy who is facing right that overlaps a sensor will go left, while an enemy facing right that overlaps sensor will go left. something like that.
Try to summarize the things you want to take into account with in the AI mentally or in a piece of paper before trying to code them. Good luck.