Exactly. In firing Comey - for any reason - Trump was acting within his Constitutional powers. A President can legally fire an FBI director. It’s not obstructing justice because: there will be another FBI director, the investigation of Russia is on going in Congress, a President can express his opinion about any investigation, and because he has the power to pardon Flynn. Nothing here is independently unlawful.
Nixon conspired to commit a burglary. Clinton lied under oath. Both are acts that are independently unlawful.
Yes. Exactly. And an FBI Director doesn’t personally supervise investigations in any case. That is the job of the Deputy Director.