This post follows directly the previous one. I’m down to a single case to prove (pag. 3).
I think I should move to Java coding, implementing the entire algorithm: map reduction (removing edges), color reduced map, restore of edges one at a time, adjust the coloring to the case to prove (e2 = red), apply Kc5 color switching, …, apply the half Kempe-cycle color switching.
Notes (pag. 1 and 2):