Parsing the puzzle of the Boy is going to take some time, because we'll never have all the pieces assembled in one place.its clear the boy has always protected his parents as you pointed out, thats clear, what i'm more interested is the nature of the boy itself, as its been pointed out, the boy has a fairy-like aura or something, but what i dont get is why he would be like that, since the boy was corrupted by femto, shouldnt he had more of a demonic presence ?, maybe the merge with griffith elevated him to a higher being, something like a demi-god, that being the reason why he can perform astral projections between other abilities he have been shown to have.
I dont know if i make myself clear this is something that it has been on my mind for i while so maybe i need to polish this idea and make a theory out of it.
The topic of the elf-like od of the Boy, revealed in this ep, is worth its own thread of discussion. But just to briefly summarize my thoughts right now, I think the contrast between the boy's initial demon child form and when he later emerges as a "pure" entity devoid of evil may be explained by the fact that he and Griffith share a body.
As the demon child, his form had evil power thrust upon it, but in essence he was innocent. As the Boy, his body was transmuted through the incarnation ceremony. So now, perhaps the evil power is relegated to Femto, freeing the boy to become manifest in something that reflects his pure and innocent essence, hence the elf-like od.