1) You say he may not have had all the information. The information Felt had was that crimes had taken place -- and he was right! Your first principle doesn't apply in this case.
The definition of a crime changes depending on a great many factors. Exactly similar activities could have been, and in fact have been, carried out during legitimate counter-intelligence operations. Felt was not in a position that could have allowed him to know for sure that he wasn't tipping off the equivalent of the Rosenbergs by his loose lips exercise. The first principle certainly does apply. Just because he happened to guess right, and that's all it could have been, a guess, probably twisted by his disgruntlement and political vews, doesn't justify his gambling with the trust the nation placed in him by putting him in possession of classified information.
2) Felt's superior was a brand-new Nixon stooge. There's no reasonable evidence to conclude that Felt could have taken any of his info to him.
3) Who would you suggest? He can't go to his boss. He can't go to the White House. Yes, he probably could have gone to Congress, but there's little expectation that anything good would have come from it.
I don't buy your assumption about little good coming from going to congress, say the intelligence committee. I don't think Nixon had the total control it would have taken to silence a member of congress, especially one of the opposite party. The only possibility I've heard mentioned for it turning out worse was the idea that if it had come from a political opponent it may have lacked the public pressure punch to get Nixon out of office. Let's not forget that Nixon voluntarily stepped down after being impeached. We have had proof in the last decade that a president who perjures himself and is impeached needn't, legally, step down. If there had been less public pressure maybe Nixon would pulled a Clinton before Clinton and stayed in office. Then maybe we at least would not have abandoned the S. VietNamese . That's a good.
Anyone with a TS clearance could have legally been trusted with the information Felt had, that includes people from the intelligence committee to people in the CIA to people in the Attorney General's office to people in the judicial branch. There were plenty of people he could have gone to.
Edit: Point being, Nixon should not have been allowed to get away with lying to cover up crimes by his staff but Felt, by the same principle, should not be allowed to get away with leaking classified information to the press.
