Amazing post!
I admire the amount of time you put into this as I'm a huge lover of any and all things marine science.
when viewed from above their dark colour blends with the abyssal depths below, and when viewed from below their bright underside blends with the incoming light from above, when viewed from the side their entire outline appears broken and makes them difficult to distinguish
this is called countershading and is used by a great number of species in the ocean as a defense mechanism as well as an offense mechanism.
Chondrichthyes have 5-7 gill slits, with most having 5 (as you mentioned the great white has).
While great whites are the perfect predator, they are more likely to scavenge for food instead of hunt prey. This is probably due to the sheer amount of energy burned in hunting alone.
Great whites are some of the only sharks to actually breach water for their prey; they have a very distinct attack when feeding technique where they come from directly underneath their prey.
Sorry, just wanted to add a little to your excellent post. :)