Planarity - replace items in a list

I am working out how to build a pavilion with cardboard boxes. however, they have the shape of pyramid trunks:the bases will be arranged towards the outside so as to be tangent plans to the surface given to me by the hypotetic customer. All faces of the pyramid trunks MUST, of course, be adjacent and belonging to the SAME PLANE, so that they can be connected together.
In my definition I have a problem: these faces seem to have suffered a twist (that is not due to a use of any physical simulator like kangaroo).

1) How can I solve the problem GEOMETRICALLY? Can I produce in another way these faces so then i’ll haven’t the twist?

2) overlapping faces, I was trying to isolate all the internal faces from the general list, as those belonging to the xy plane do not seem to have this torsion problem. How can I delete double faces?

3) replace item in a list. I ask one last question: I have isolated the normal vectors of the base vertices of the surface since these faces of the boxes must, of course, rest parallel to the ground. I did this by removing the z value from the vector components. How can I re-insert these new vectors in the same position as the general list of vectors normal to my surface?

I’m sorry for all these questions and thank you so much to anyone who can help me!

I post here a capture of the shape and my gh file (25.4 KB)