You would think they would have someone go and check with the land bound god every once in a while. Also if the city was moved 100 years ago, who the heck moved it? They've made it clear that the girls aren't technologically advanced since they don't live long enough to pass on a proper education system. The only people who could probably move it are Kai, the 3000 year old witch that mated with the last male, and Galia. Considering Galia was the one who made up the rumors about herself 100 years ago at the same time the city was moved and also started her fasting at the time, that would leave you to believe it was Galia, but that doesn't make sense because the sandstorm was used to prevent her from accessing the city. This would make a lot more sense if they spent more time talking with the bound gods instead of doing things without any insight.
At this point it seems like all of the girls are genetic clones of Nishina / Deeply Jealous God and that killing her "fixes" the curse by no more girls being cloned/born. The the other portion of saving them, mating, is made the completion of the genetic materials required for the clone to be completed. The Kall were likely initially made to complete the genetic code for the clone women, but either they failed or overtime their artificial solution became poison. That's the only thing that makes sense for the Kall to stop appearing as soon as a male shows up. Why offer the synthetic solution when there's an all natural source available.