The olive oil keeps the paste from drying out and I think makes a better "smother" effect... If you ~want~ it to dry and have great results without it, you should leave it out. Daily that might dry out your skin though... I use moroccan or jojoba oil to moisturize afterward, but they are really too expensive to use in the paste.
This does get some serious junk out... Make sure u get just under your jawline and glands.... I even very carefully get under and in the corner of my eyes and bridge of the nose. That seems to draw fluid as well as grit etc...
Yes absolutely save it! I've never had a problem with it going bad. Good luck and glad I could help : )