The max wifi transfer speed for the WFD is 6Mb/s so a 1.3Gb file is going to take some time.
Wireless coexistence only works with iOS 7. If you are using a Samsung device this setting will not be applicable.
DRM protected files are not supported by the WFD/WMD software so you will not be able to stream DRM protected content.
@monicakm and Marvin
If you have having issues with the wifi dropping you can try disabling auto network switching and changing the wifi channel the WFD uses.
Disabling auto network switching
http://kb.sandisk.com/app/answers/detail/a_id/13458/kw/auto%20network%20switching
Changing channel
http://kb.sandisk.com/app/answers/detail/a_id/14656/kw/WFD%20channel