definitely feels a bit like Doctor Strange in Infinity War. He knows there's one way to win and even if he dies (at least temporarily) they have to do it.
Agreed, even if he doesn't exactly how how to kill him, he at least has an idea for what to do. And I wouldn't be surprised if that idea involves some sort of sacrifice to the Old Gods.
The 3ER can only see the past/present, as far as we can tell, yeah?
I don't think Bran knows for sure how to kill the NK, as it has never happened before. He has some theories about things yet untried (his response to dragon's fire), but he's still taking a risk
I can't say unequivocally that he knows for sure because it hasn't been explicitly stated, but he likely has some sort of plan. Everyone keeps focusing on the Lord of Light when it's the Old Gods who protect the Starks. The 3ER draws its power from them. If the NK goes down their power will be involved for sure.