There are 'commands' Killua needed to use for this arc regardless of how it happened:
1. Cure Gon. (we know he can't possibly pay back the pestering cost for such a wish)
2. Prevent Nanika from coming back again. (by definition you wouldn't need to pay anything back after that so might as well be a command)
Killua firmly believes Alluka will only be safe if Nanika is gone. So after asking for a ridiculous free wish his next wish basically is 'thanks for coming but goodbye forever'. And then he argue about not wanting to use Nanika like a tool? Does having a minor wish like teleport somehow makes Nanika feel better when Killua tells her to never come back? If you say it matters then Killua must be one of the biggest hypocrite I've seen, and he's not supposed to be such a character. All along he's been someone who is definitely willing to accept sacrifices to get things done. If he was planning to dump Nanika at the end anyway (since this is the only way he thinks his family will leave him alone) then he's already accepting the fact that Nanika is a neat tool for him to get free wishes that he's going to drop as soon as the last big wish is done (cure Gon). There's no point to go through all the needless danger (Ilumi was trying to kill Alluka, which is clearly something that could've worked) just to score 5 more affection points with Nanika before banishing her to the void.
I just noticed one of the really crazy things in this arc. After curing Gon, Killua went ahead and told him everything about Alluka, including the fact that he has unlimited wishes, because clearly Gon is trustworthy even though Gon is a guy who randomly blew off Killua whenever he feels like it. On the other hand, Killua is unable to share this secret with his father, Silva, who is a role model father not only in HXH but possibly across all manga. This is despite the fact that Silva called off the lookout order after knowing Alluka's power. Killua also notes that Silva also still thought of Alluka as a daughter by the toys, and Silva tipped off the fact that Ilumi was willing to kill Alluka. Had he simply tell the truth to his father, Silva would've said something like, "Son, your brother isn't someone to be reasoned with so you better make a command powerful enoguh to make sure he can't attempt to kill Alluka or brainwash you", and there are any number of possible commands that can do this rather easily with Alluka's power. So all this is self-inflicted because Killua cannot trust his father, who has done everything possible to help his son. Contrast this to Gon, who admires and trusts Ging unconditoinally even though Ging abandoned him when he was a baby, and had a deathtrap waiting for him in Greed Island with Razor.
