use MPeg Streamclip to transcode the file to a ProRes format,
Prores422, say,
keep the frame size the same, or un-scaled.
in FCP, open the clip’s item properties, and tick theAnamorphic box.
“Why would a file that is sd dimensions look ws in qtx (shows as 1024 x 576) and 7(shows as 720×404)?”
this is the nature of the anamorphic process
all SD video is actually 4/3.
16/9 images are squeezed when recorded as SD, and unsqueezed when played back.
nick