1. Yes, the unit designer is in-game. The version at PAX had a "kingdom button" which had the unit designer in it. It was pretty much the same idea as the galactic Civilization unit builder. But as scorpia suggested, if you want to use something that is not part of of the base game, you'll have to likely create it out of game (or download it from stardock's custom content servers, which we've yet to see how works.)
2. scorpiana covered this on well enough. All I can contribute is "I played with it at PAX... it was accessed from "workshop" on the main menu, then you click "tile editor" "
3. does it matter? something as simple as a name (i.e. week, munth, year, season, etc. ) can be changed pretty easily. Hardly a selling point.
I honestly don't think they are even 100% sure how turns are going to function at release. By that I mean to suggest, I am willing to bet money that the way turns function now, and the way turns function at release will not be the same. Of course we'll see. But there are many factors such as AI and Multiplayer that could make changes on how turns function that have yet to be implemented.
