1 –How is Itsuki a pure Shinigami while having his Zanpakuto's absorb a hollow?
Well, I believe that zanpakuto's are their own entities. Although they are formed by a Shinigami's soul, later on the are both, part and not part of a Shinigami. It's a bit like Ichigo, he is ultimately a human but has the power of all the races
NewBRage has explained it rather well
"Okay, writing this once for all to understand. Zanpakutos are not made from your soul, they are linked to your souls. All Zanpakutos are personally forged through a special method by Ōetsu Nimaiya (AKA: God of the Sword) which allows the user to link his soul to zanpakuto which acts as a medium to release one's inner powers. Zanpakutos are given in the Shinigami Academy after which the person needs start to meditate in order to link one's soul to the blade and slowly start merging with it. Only two people in Bleach completely merged with their zanpakutos: Ichigo and Aizen. Only if Itsuki will fully merge with zanpakuto, the hollow powers will be embedded in his soul."
Or how 28th00 has explained it
"No, Zanpakuto's are formed from an Asauchi and a fragment of their own soul. They're connected because they used to be the exact same being, but are not anymore. Shinigami get most of their power from the Zanpakuto, minus things like Kido or Shundo.
Think of this as a loophole?"
Whichever you find suits you the most.
– Legs and the 26 people who like his comment, Slesk
2 – Nel?
Well, I came to the conclusion that Aizen must've made a trip to Hueco Mundo before the start of the plot. This is because when he ultimately betrays Soul Society he is already Hueco Mundo's ruler. This ended up resulting in him having already creating the espadas before the plot in where Nel loses her powers before it as well. I could be wrong but if I am wrong, with the power of me being the author I will give the reason to butterfly effect.
– I remember seeing the comments somewhere
3 – Ichigo as a disciple?
I'm still currently thinking of that as I'm in two side of that. It would be cool but the plot armour he had is OVER 9000. So, yeah, I will see about it.
4 – If his zanpakuto absorbs the hollow will it change his its form?
5 – How long has he stayed in Hueco Mundo?
– Dao_Of_Battle, Lomyril, Albanzekiraj
6 – Why make another experimental hollow for MC to get powers and what will happen to the Hogyoku?
Well, I can have Itsuki create another hollow but I found it easier for Aizen to do it. Why do the work if someone else can do it for you. As for the Hogyoku, we will see.
7 – Quincy Powers?
I don't know. The prerequisite for these powers is for one to be human and, ultimately, Itsuki is not. Plus, I don't want to complicate it too much, so, I'll see.
8 – Will Itsuki train others in the way of the sword?
Yes, his children :P
As for others, I'll see.
– (2nd) GeniusNovelist
9 – World travelling?
I've done a poll before and majority was for this novel to be purely bleach. Afterwards, I don't know, ill do another poll then as well.
10 – Can you show Itsuki's prowess in Kido and Kaido(Healing arts)?
Yes, in future chaps.
11 – If his zanpakutos are taken away, will he still have his hollow powers?