Remove Details tab and place Details button on the same row of Close button. Similarly to the GTK+3 About dialog.
No.
It would save screen space, especially in notebooks.
Yes, that would be a valid reason; But my plans are actually to add more tabs in a future release, e.g. a radar map whenever that will be.
The following layout may be good. [Details] [ Radar ] [ Close ] [Credits] [License] [ Close ] I would not want more than 3 buttons, so I back off if more than 3 views (Forecast, Details, Radar) are planned.