If you use the right click scale to frame size command or if you have the default scale to frame size option on it will show the scale as 100%. The scale value changes only if you manually set it.
The thing is the resolution of the still is way bigger than the resolution of the timeline. You can right click the still image in the timeline and choose to scale the clip to fit. You can also set the automatic scaling as default in the options.
You can use Adobe Media Encoder or Prelude to do blazing fast transcodes from the original files. Redcine X is insanely slow. If you want to edit from the originals you have to deal with the fans.