D2R on 5k display

I am running D2R on an 27“ iMac with 5k Retina Display on Bootcamp. At the very beginning the game crashed at start-up or freezed. Finally I reduced the Windows screen resolution to 1920x1080 and could fluently play in both, full screen and window mode.
The strange thing is, that in the game options just the screen resolution from the Win 10 is taken and no others selectable. This is very inconvenient, since I always have to switch the Win 10 screen resolution when playing. Also the Radeon Pro application does not allow an individual resolution setting for the game.exe.