At the time, I don't think Sidious could win. But in his prime, Sidious destroys Plaguies.
On the topic of Sidious' death. He died due to arrogance, which has killed many Sith. And it's not like he was falling for days. His body was destroyed only seconds after falling. He didn't have time to react.
I don't think Revan has a 1% chance. Sidious is a master of precognitive abilities and could see Revan coming from a mile away. i don't think Revan could plan for everything Sidious can do. But it is your opinion and I respect that.
revan had advanced precog as well. at this point its just best to leave it up to fate (tho we all kno revan would win)