You can't use that card for everything. There are well established geopolitical red lines in the sand where the nukes would be launched, have been for a long while, even during the cold war. Some poking and prodding is generally accepted, and while it will lead to escalations, it'll not lead to war. Only differing leverages politically. If on the other hand, you start waving your red nuke card for every issue you want your opinion to be accepted, then it becomes worthless. Just like in the boy who cried wolf.
Where is the line in the sand for the baltic and scandinavian states wanting to join NATO?
"If you join NATO, we nuke you"
"If you stop trading with us, we nuke you"
"If you don't stop trading with the US, we nuke you"
"If you don't join the Russian Empire, we nuke you"
Sure, russia can bring all those, but I doubt anything but the first one is even considerable for a state. And even then the more you wave the card the more attractive the first option of joining NATO becomes, because once you're in, Russia can't nuke you.
No it doesn't. You merely have to show that you're willing to resolve conflicts peacefully first. Generally so far this has meant "don't be in any conflict", but nothing stops participants from agreeing that, for example, Finland is always willing to resolve things peacefully. And after all, the threat is "if you join NATO", which means while joining NATO they aren't in a conflict, only once they joined.
They're still waving the 'we have nukes' card, so states are still scared though.