Sure, Soma went to cut himself off from chaos, but I don't believe the rest is correct. The castle is clearly shown to be an independent entity from Dracula. So much so that Dracula got separated from the castle in 1999 and the castle kept existing. It's existence doesn't depend on Dracula, it depends on chaos. Cutting Dracula's soul from chaos doesn't cut the castle from chaos.
When Soma cuts the connection between the "evil spirit" and chaos, the castle ceases existing not because "the connection between the castle and chaos was severed", it wasnt. It disappeared because it was resealed in the eclipse by members of the church. If you check the Library in Dawn of Sorrow, it says that the castle is still inside the eclipse waiting for a new master. In the novel, it says right at the beginning that it was resealed right after Soma cut the connection between himself and chaos.
TL;DR: The castle disappearing at the end of Aria is not a consequence of Soma cutting off the connection with chaos. It is simply the castle being resealed inside the eclipse.
We don't know if the castle crumbled or not at 1999 when he lost his connection with the castle, he could've emerged again inside the eclipse at 2035 like it always does. Also it doesn't depend on Dracula, but depends on Dracula's magic that yes, come from chaos. It seems that Dracula's magic was in Castlevania all these years, we can see that on Aria throne's room dialogue with Arikado, also Graham uses it before us.
I know that Castlevania was never truly destroyed at Aria's ending, but it is a consequence of Soma cutting off the connection and also because the eclipse ended, no need to seal again something that stills sealed. Now I really don't know if Dracula's magic returned to the castle or not after that, or if the castle started to drawn energy directly from chaos from this point on. Surely you can also be right and the castle drawn energy from chaos directly, after Dracula's death.
Even so I see cutting something from chaos as the same of cutting a wire, you can still connect it together again. Thats why I really think that Soma cut Castlevania and his soul from chaos, someone could easily "turn ON" the castle again with a ritual, but it would be still needed to wait an eclipse and it would be inside the eclipse yet.
OK, the first citation is not an explanation of what the castle is. It is explaining the belief held by Graham's cult that lead them to become a literal part of the Legion castle. They believed that, if the castle was whole again, THEN his body and soul would return (as Graham, no less) because their belief is that the castle is a part of his body and soul.
And we know they were wrong -- Aria proves it by showing that even with the castle back, Dracula's "body and soul" are not. They exist as separate entities. EVEN THOUGH I agree that the castle is a manifestation of Dracula's magic and is a reflection of his will (and maybe his soul too, why not), I do not agree the castle is "part of his soul" as in "it depends on Dracula's soul to exist". It does not. The castle was separated from Dracula before, and it still existed just fine.
The complete quote:
Those who adhered to Graham Jones were those who were obsessed with the thought of an impactful end.
The world would soon perish. For their fallen neighbors, they would change themselves.
In order to become the body of [god] destroying this unclean world in order to create a new world together with [god].
That kind of thinking influenced this group of fanatics.
Their founder was born on the time that Dracula died and had received a degree of [power]. That was the man named Graham Jones. He had a charisma that attracts people and was practicing real magic.
He as the real dark lord and ----- also as a [fallen] human----- sought to create a paradise [Genesis] which was blindly believed to be possible.
And that blind belief still continued on unchanged even after their founder died.
It was just their story.
“Dracula’s castle, in other words is the embodiment of Dracula’s magic, a part of his soul and body, their belief in them being [fallen] and a part of [Genesis}.”
The second quote, about Death, doesn't imply Death is the embodiment of the concept of death of all things. It implies Death was born from the "human death" part that comprises part of chaos. Like "Paranoia" was probably born out of the "human paranoia" part that comprises chaos.
This explains why Death intends on influencing humans towards death (as a Shinigami does in japanese culture), and not that Death is death as the natural concept.
Text with "" is spoken by someone, that someone being Olrox, before that it was being really explained only their belief, when Olrox started talking he said the definition of the castle and their belief. Surely it was been proved that Dracula isn't needed anymore to Castlevania exist, and that is exactly why he says that it is a
part of his soul and body.
Its highly implied in Aria that Soma isn't whole until he absorbed Dracula's magic from the castle. So it can be a example.
About Death, like I said before I don't think it too, but I know what it implied on the text and it wasn't really it, not at this moment. They could've wrote "god of death/shinigami" like before. He said "Human death" because he was explaining to someone about a certain someone death, chaos come from humans alone and they say human a lot in this novel. It seems to me that Death isn't the "death concept", but really is a embodiment of the concept.
A concept doesn't really need a body to exist, so even if you destroy it, it will still happen, like Paranoia. Its really deep man, thanks for opening my mind even more. That's why I love these debates and conversations. Because if we agree we learn, but even if we disagree we can open more our minds.

I think I don't need to say, but these and future posts are only my opinion.