That the reason you must de-interlace to clean the blending. The de-interlacer of Photoshop is not the best one. You better do it in FC, AE or Shake.
The change in the aspect ratio is normal because your watching with an application that do not interpret aspect ratios. Is just a matter of displaying the picture, because you still having the same number of pixels. If you bring your still to FC, Shake or AE and you set the correct pixels-aspect will look weel in your monitor. In Photoshop or QT they will look defformed.
Salud,
Rafael