I think in the movie Spock Prime gave us a big hint of what he'd do with all his "special" information. He took a gamble (he called it an act of faith) when he chose not to aid in stopping Nero, even though he could've been of great assistance. In this case, he wasn't even holding any future knowledge of events. His intervention could have been justified even with a temporal prime directive. But he opted out.
He risked the fate of billions of people on Earth that Kirk and Spock would succeed without his aid, just so Kirk and Spock could see all that they could accomplish, together.
If he was willing to allow that, then -- .
Maybe...but don't you think that decision was based on running into, of all people, Kirk, and Scotty?
Besides, if you follow this to it's 'logical' conclusion, then Romulus will be destroyed again.
edit: and re: above about Star Trek IV..."Go back in time, get some whales and bring them back to save Earth" Compared to 'levels of violation' I would call that almost Janewaysian or Kimsian. The only difference being how little time has passed.