Those fights are fairly easy on level 20, so they should be possible on 18 (though your hit points seem a little low).
Assuming you have level 1 of the healing spell (available at level 17 IIRC) and a few potions, I would either have Sassan attack, or summon if that doesn't work out. If you save first you can try something else if one strategy doesn't seem to work very well (I had her heal me, but didn't need the help).
My creature seems to be doing better with Fireball 2 than he did with Rush Attack / Fatality 6; as soon as I find a mage head with Magic Missile I'm going to give that a try. A warrior creature is a reasonable distraction for a couple warrior opponents, but with larger groups or groups with archers and mages he would be as good or better a distraction as a mage (slightly less running around) and the melee damage he can do is not that great compared to using magic.
