parametric tetrahedron vault

Hello, I'm trying to make a parametric vault composed out of tetrahedrons. This vault has to be such that i can increase the number of tetras in every row but at the same time being able to adjust the angle of each tetra to fit exactly with its adjacent tetrahedron. I managed to get the basic shape but I'm having trouble to making it possible to have the angles of the tetras change accordingly as i adjust the number of tetras. Would really appreciate any help. 

Second problem is to apply these to an arc. On a flat vault I simply used a square grid and assigned a dispatch command to have the required effect.

Many Thanks :)