many ideas to test.
the 4n n=123 with deuterium as in iwamura make me thing of ded fusion, but in 1D=ded 2D=ddeedd and 3D=dddeeeddd , with cubic geometry
to make it look logical I imagined that electrons were split into two lobes, half of which would face a void ( or an heavy atom like with iwamura) between 2,4,6 nucleus, whether it is 1,2 or 3D bar/square/cube... and all would collapse/fuse...
anyway I'm not physicist and maybe cube symmetry is absurd here...
maybe the n=2 is not plane/2D but tetrahedral as you suggest
I just feel that geometry, because it is linked to CoM and thus to the absence of energetic gamma (and tritium), is important.