I did find something that could go wrong in your approach:
The red Node compares surface area. but what if the area of interior and exterior side are the same?
I replaced it with the green node… but my question is are the Surfaces always ordered the same?
Is surface at index 1 always the exterior side?
See attached image below, i marked the exterior side with green and red lines. The green one is good and the red ones are placed wrong. The family is to long to fit the wall, this is just because its easyer to see whats going wrong until the script is flawless 
Would u know how to place family’s on face next to / above a opening in wall? I dont know how to get acces to lines or points of the wall opening / window.
This is the topic: