I'll take a stab:
1) News is an account (story) of an event. The degree with which it is "true" is the degree with which it holds the events to account, and the degree with which the news organization/publisher holds itself accountable for that account/story. Good news is accountable and provides accounts of events. "Truth" is the wrong focus; "fact" is far too malleable (hence the status-quo legitimacy of "alternative facts"); accountability is the goal.
2) A journalist is someone who writes accounts/stories for a news organization/publisher and, in turn, is held accountable (either professionally or legally) for their story. Anyone can be a journalist, but few are willing to hold themselves to the standards of accountability good journalism demands.
3) The division between news and op-ed is marked by the degree and nature of accountability. News organizations are accountable for the news. News organizations call for op-eds and those op-eds have a different standard of accountability. That's why we call them op-eds. If a news organization will not hold itself accountable for a story then it is an op-ed.
We are far too focused on "truth" "fact" and "objective vs subjective". Instead we should focus on what the use of journalism and the news is. The use is accountability. And the special nature of news and journalism, what differentiates it from fiction and bullshit, is that it is also held to standards of accountability.