Obi-wan's own skill was keeping him alive there. Don't start, because even Mace considers Obi-wan one of the greatest living saber masters
Sure Mace does, yet your argument is still invalid because Obiwan knew every move Anakin had, which has no effect on Obiwan's overall skill.
Kun was the strongest of the two. Why else would they name HIM Dark Lord and not say 'fight it out', since the Sith apparently were fine with death duels when power was not determined. [/B]
Kun was stronger in the force no doubt, but at that moment they were equal in saber combat.