I concede that Revan had the resolve to get what he wanted, but he wasn't evil, or insane. He didn't truly want to activate the mass shadow generator, he was a Jedi after all. It was a last resort, and last resorts would not have been necessary in a winning war, which is what it would have been if the Jedi intervened.
Yes he was and yes he did. The Mass Shadow Generator was all part of his carefully laid plans to not only annihilate the last of Mandalorian Resistance but only eliminate any Republic and Jedi forces that were not 100% loyal to him by then. His tactics during the war were absolutely un-Jedi like (such as deliberately sacrificing his men), and the record left behind by him during the Mandalorian Wars (such as the hologram on Kashyyk) indicate that even then he had a very sith like attitude.
The problem with your argument here is the council disagrees with you, they accepted responsibility for Revan's actions and admitted they were to blame. (Zez-Kai Ell also adimitted they were to blame for the fall of Ulic and Exar Kun.) Your also mirroring the arguments of Atris. Who also believed that Revan was a traitor, and that the council was not to blame for his teachings. Yet they disagreed with her, as they would disagree with you. They admitted that they were arrogant in their teachings and had become misguided, they made a mistake. Joining the war may not have been the solution, but doing nothing certainly was not.
If the Council accepted any direct blame for the fall of Ulic, Revan and Exar Kun then they were wrong to do so. Just like how they were wrong about most everything else in the game. That was the whole point of Kotor 2, it goes out of it's way to make the Jedi Order wrong, regardless of how much sense that made. None of those people used Jedi teachings in their fall. They specifically went against what they had been taught by the Order when falling to the dark side.
It was not Obi-Wan's fault entirely. But arguably the Jedi were to blame. After all they taught him everything he knew, and let him be trained at such a old age. However this is a different situation, were Anakin was more involved in his own fall e.g. his revenge against his mother, and his relationship with Padme. Sidious also played a big part in coaxing him to the dark side.
But with Revan, the inaction of the council forced him out of the Order. Unguided by the Jedi and enraged by the Mandalorians, his fall was inevitable - only the Jedi Council could have prevented it. Whereas in the case of Anakin they would have to remove Sidious, Padme and Shimi from the equation, which was impossible. Removing the Mandalorians from the equation was not.
Apart from the retcon of Revan meeting the Emperor, nobody forced Revan to do anything. He has free will, he made the choice to leave the Order and join the war. He made the choice to do all the things he did until he was further corrupted by the Emperor. Heck, I think Kriea seems to say that he'd already made up his mind about Jedi teaching even before the war.