It should be noted the interior mapping example you posted doesn’t use cubemaps. It uses a 2D texture atlas, one I created and posted the example shader code for here:
It’s based off a technique used in SimCity 5, but for which working code was never shown, so most of those examples are built off of the above post. It also has example shader code for a cubemap based version of the effect which is what your code is attempting to recreate.
Obviously it’s not in node graph form, but it might help? I didn’t see anything jump out at me when looking quickly over what you posted above.