I would say it's perhaps never been higher since the Cuban missile crisis.
The West being aligned with Ukraine would prevent Ukraine from getting nuked in an extended conflict.
That being said, there would have been no extended conflict for Ukraine without the West's assistance, they simply wouldn't exist without the international assistance, reducing the chance of Russia using a first strike against Ukraine to 0.
Don't underestimate Russia but don't overestimate them either:
Russia lost against Afghanistan already back when they were a superpower and had Ukraine on their side.
They will lose this time too even if they are even dumber this time and choose to waste all their conventional forces there.
The mujahedeen fighting Russia in Afghanistan also had Western (US, particularly) support.
So I think we’re still quite a ways off from that level of threat.