@Sylph I was (and still am) in the same situation as you, and I followed a similar approach: I added unknown vocab words to my Anki deck if I got interested in them (“I would like to know this!”) or if they annoyed me too much (“Why do I have to look this up yet again…”).
And this helped me soooo much already!
(And then, I thought that I’d be able to add ALL unknown vocab words from Kiki to my deck, but I only managed to do that for the first chapter
)
Can’t you limit the amount of words you are learning every day?
I don’t mind adding however many cards to my deck, as I only learn 10 per day (and as I’m learning each word in 3 directions, this means ~3 new words per day only). My deck just serves as a buffer, and when I see a word in more than one book, I push it to the top to learn it more quickly, this way shuffling my deck around basically every day…
Yes! Initially I did not modify them as much, but recently I read the documentation a bit more and adjusted lots of stuff. But:
I think I’m on the other end of the spectrum
While I notice that I can pick up new words much more easily than when I started out learning, I still like to go much slower than WK… I think WK’s SRS is fine for me up until Guru 1 or Guru 2, but then it gets much too spaced out for my poor old brain
So I need to take things more slowly.
Yep, same here
I don’t mind having a word come back to me in 10 years’ time 
Yes, that’s really unfortunate but true.
They recently switched their help system to a new platform; it’s now a Discourse
and amazing people have contributed with long writeups of how stuff works etc. Also if you have a question, they quickly answer (at least in my case). Might be worth checking there as well if you have another question…