Putin doesn't want a war. And it's a moot point because there isn't going to be one. Vladimir Putin is the most powerful man in the world right now (a position previously held by every U.S. President since 1945). He's going to get what he wants.
He'll continue to support the separatists, while denying it and the West will continue to issue toothless sanctions that don't affect their ability to buy much-needed Russian oil.
Eventually the fighting will stop. Western Ukrainians are already getting war-weary, tired of being told their sons are fine despite not receiving letters or phone calls in weeks. Ukraine will split in two with Donetsk the new capitol of Novorussiya. If Putin plays his cards right, he'll have a pro-Kremlin government in Kiev as well.
The West has no appetite for all-out war with Russia.
Russia just invaded yet another country, probably has lost hundreds of soldiers while mothers who complain are called "foreign agents" (which is a threat). Tsar Putin is going to be eyeing other "fake countries" he thinks are really part of Russia after this.
Putin also has no appetite for a war with the West. It would be a mess, but he would lose. The Russians are playing poker with a wimp.
Don’t think for a minute he wants his country ripped up any more than we want ours torn up. At some point in this there will be an eye ball to eye ball stare down. It may not be the Ukraine, but somewhere along the line of separation between the East and the West he is going to overstep.
The thug isn’t going to be satisfied enslaving part of the Ukraine.
And Russia’s negotiating position (certainly with Europe) gets stronger the closer things get to winter (hint: natural gas and oil).