Skimmed through your post.
City and Stones have not entered negotiations. Everton have been contacted, City have been told to wait until after the Euros and that a lot of money will be required. Money is of no issue to Everton anymore, transfers are purely to dodge the slalom that is FFP. All this I know to be an absolute fact.
I was very hopeful of it a month ago. I was sure that Lukaku was going and Stones would stay.
Now, it appears as though the opposite is the case. Funny how things change. I assume Koeman has made a decision and deemed Stones expendable in order to improve the squad. I can see why he'd value a proven 25+ goal per season striker over a defender, but I would honestly prefer if we kept Stones; he has a high skill ceiling.
As I've said, the investment has made money no issue. The issue now is FFP and Stones' sale would allow Koeman to make the transfers he needs to improve the squad in the areas that need improvement.
To summarise what I said above, it is likely that Stones will be sacrificed for FFP, which is why you haven't been told "not for any price" but rather "wait".
It's not just Stones being away at the Euros which is delaying these negotiations. Koeman has a list of targets and the Euros are preventing him from negotiating for those players too. Once he can summarise who's available, who he can get and how much it will cost, any negotiations over Stones can begin.