Did a lot of your UI suggestions immediately, and will do the rest later.
Endgame popup:
It's kinda hard to decide when tooltips + feedback/animations are enough and when a tutorial popup is needed.
I think I'm going to try and make non-diegetic tutorial popups feel less like dialogue popups (place textbox near what they're about, text appears instantly, different look)
And then try and teach the player to look at tooltips when stuff gets framed, so that some of the tutorials can be dialogue + framing the UI elements that dialogue is talking about.
So definitely going to add something for Endgame, but it might not be a full explanation.