Of course, Dooku left the Jedi Order after TPM. Good thinking. I think Sifo-Dyas was killed before TPM. It would make sense. We could say that when Anakin say no one could kill a Jedi, and Qui-Gon said he wished that were so, the Jedi Master could be thinking of Sifo-Dyas. I have always believed that Dooku was only using the name Sifo-Dyas. Jango said he was recuited by Darth Tyranus. That poves that he was using the name Sifo-Dyas in my opinion. When Darth Tyranus is talking to Obi-Wan, I thought he meant something different than what you were saying. I'm under the impression that he is loyal to Palpatine. Tyranus did say, "You must join me, Obi-Wan, and together we can destroy the Sith!" That was just something to fool Obi-Wan for some covert reason. When Tyranus said, "He came to me for help, and told me everything," I thought he was referring to Darth Sidious aka Palpatine, not Nute Gunray. It would make sense to Obi-Wan, Mace Windu, and Yoda after all to know that he was a Sith.