Another amazing piece of content @RahiWatching 
This is exactly the type of analysis I enjoy.
Here are a few things to consider in addition to your calculations. The effects of the Nova Blast can vary even within the element and the Toa can control these effects even after the blast is already set off, albeit it is very difficult for them to do. You assumed a two dimensional plane with a third dimension of 1 cm, but we could also consider a spherical blast area using the same radius.
To add to the reserves of elemental energy, Toa can also draw upon the existing element in the environment to boost the Nova blast further.
The only Nova Blast we see fully performed in story had several special things about it: Gali Nuva first “silently” released the Nova equivalent of elemental energy into its blast radius and used it to extend her elemental reach and condense all of the moisture in that area. She then materialized all of this water which she drew toward her in a form of a gigantic circular tidal wave which leveled all of Karzahni. While keeping herself and her allies from drowning using her KauKau Nuva, she was manipulating the currents in her immediate location to try and wrench the Staff of Artakha from Icarax’s hands. However as you can imagine her control under such extreme conditions was hampered and she failed to do so before Icarax escaped.
What we can gather from this is that a Nova blast can have various forms, can be boosted further using environmental resources and can at least crudely be controled during the actual blast.
Nova Balsts become even more extreme when we take into acount the predicted gravity and material density of the MU/Spherus Magna.
To finish my commentary on the extremity of the energies involved in a Nova Blast, there is a quote implying that the Nova Blasts have even greater planet-wiping extinction event potential than we were led to believe and the domes of the MU are actually designed to restrict and isolate the power of the Nova Blasts to a smaller area.
Happy nightamers Agori, I hope Marendar comes to save you.