I wonder how you picture NATO intervention without WW3, could you explain? IMO Nato intervention means a military confrontation between NATO and Russian forces.
Also I don't agree with your second point. 'Any sanctions left' here means actually more than the entire packet of sanctions that the West has taken so far. The West spends hundreds of billions each year on Russion gas and oil. Sanctioning this would seriously hurt the Russian economy and Putin's war chest. Yes, it would also hurt the European economy, but surely many magnitudes less than a WW3.