(3) It’s not an impeachable offense. There is no such thing as an “impeachable offense.” Impeachment is as impeachment does. It is a political process that can be undertaken for good reasons or bad reasons.
You could, today, make the argument that Congress had no choice but to impeach Bill Clinton because to not do so would have established a precedent that encouraged presidents to break the law.
Similarly, you could argue that even though Bill Clinton perjured himself, prudence should have led Congress not to seek his impeachment because this action contributed to a cycle of political destabilization that weakened important institutions.
What you cannot argue is that perjury (or obstruction or collusion or whatever) “is not an impeachable offense.” Because there’s no such thing.
Impeachment is a political and prudential argument, not a black-and-white definition.