1] Elaine is still alive, plenty of evidence of that.
   2] Since Aurora went bonkers, most likely Nemfected after Elaine sought refuge at the Summer Court after Elaine fled when Harry killed Justin, it is either a real coincidence or Elaine is infected and passed it on to Aurora..
   3] For all of that, no, I don't think Elaine is Kumori.

Evidence for E = K please.

Unfortunately our sample size of cats in the Dresden files is very small. We have Lions (Nimean and otherwise) And the Malks. And the Mister.

Mister in being a Changeling who has decided he is fine as he is, is ultimately more ‘Real’ in the spiritual world than other normal beings, he is the feline equivalent of the Faithsaber in that regard. Ghost Harry was therefore able to interact not with Misters body, but with his spirit which is exactly the same as his body as shown by Harry’s third eye. This is why he is so deadly to the Little Folk, it’s not just his physical mass, it’s his spiritual mass as well. It’s why he wasn’t phased by the Nimean Lion possessing his body, it was fun whilst it lasted. His hatred of dogs may date from his time with Lea, so having a go at Cerberus was exactly what he fancied.

Forget about circles, all you need to summon Mister is a bag of catnip.

The reason the Council are still alive isn't because the world is badly written, but because they're falling from a great height in slow motion. It's been foreshadowed that they're on track to either end or go through a transformative reorganization, though.

On technical level with fae queens and arch demons in that they would require the same sort of circle macfinn needed. A being of flesh AND spirit.
🤔 Though exactly why they wouldn't disrupt the circle.. can't wrangle if that means they have, or don't have free will, or something else more chaotic altogether.

He would spend the time and effort to get a real one.

Honestly I suspect the Archive's function as the mortal-side conductor of the oblivion war was something Jim came up with after Death Masks, not something he had in mind from the beginning. He's said his initial genesis for the archive was just wanting to write a creepy little girl character. It's sort of hard to justify a being as vitally important but (mostly) mortal as the archive ever hazarding herself in field work. How do you logically go from "My job:  use intellectus to keep track of all human knowledge to watch for cthulu cults" to "My task: get involved with random supernatural disputes all over the world."

That said, I suspect should the Archive be killed without an offspring, that's it. I imagine that's a tempting target for the enemies of the Archive.