the jedi killed the other hunt champs. The chancellor, like most politicians, did not look into the matter and just did as the jedi said. Plus, keeping the Chancellor alive, showing the reublic that you're not completely in the empire's pockets, means i can play both sides and, hopefully, acquire bigger credit opportunities.
Murdering others is a disservice to your fallen comrades. Jun Seros was the responsible figure, the Chancellor was just an inept chancellor.
No, as the chancellor it's his responsibility to verify the fact before he declare it publicly, like he said he deceived public and was going to be removed.
You are still the republic's enemy and what's good for you? The Jedi would not forgive you after you killed 3 masters, the new chancellor would not like you either.