Ukraine - World War III powder keg?

In World War I, the Balkans were the powder keg of Europe.  In 2014, events in Ukraine began to shape up much like they did before the previous world wars.  The invasion of Crimea was much akin to Hitler's invasion of Sudentenland to protect the rights of ethnic Germans.  But many wonder, how could such a situation ignite a major global conflagration?  Former Soviet President Mikhail Gorbachev had a stark warning that a cold war could ignite a hot one.  One has to read between the lines in Putin's bellicose statement that the fall of the soviet union was the greatest geopolitical catastrophe of the 20th century.

How could something like this happen?

The answer is simple.  As a result of increasing isolation, Vladimir Putin will increasingly turn to enemies of the West.  Vladimir Putin made the analogy of a cornered rat, where it jumped at him as a child.  He finds himself in that situation at the moment.  If he backs down, he will be perceived by his people as weak, leading to him suffering the same fate as Viktor Yanukovych.  He wants to avoid this at all costs, therefore he is walking a tightrope.  Despite the devastating impact of sanctions, he cannot back down from supporting the separatists in Ukraine - therefore he must double down.  His doubling down will force him to become more allied with rogue states, as western powers inflict an ever increasing cost on the Russian economy. Putin wants to look decisive, and he hasn't been.

From the onset of the Minsk Accord, the flow of arms into Ukraine continued unabated, buying time for the separatists to regroup, and benefit from training by Russian regular troops.  Viewing that Europe had little appetite for increasing sanctions, kremlin proxies resumed their assault on Ukraine - the Mariupol Massacre, and taking of the Donetsk airport - to probe the reaction of the west.  The real danger lies in the aims of Putin - to annex Eastern Ukraine.  Three possible scenarios exist for a military confrontation with Russia:

1) The province of Zaporizhzhya is home to Europe's largest nuclear power station - and stands in the way on a land corridor to Crimea, and another one is located in Mykolaiv.  Spread of the conflict to this region would be very dangerous - if Putin's proxies can bring down a passenger airline, they would be equally capable of shelling a nuclear power station.  Creation of a nuclear disaster would bring a swift military response from the west.

2) Russia could provide rogue states such as Iran or North Korea with nuclear weapons technology.  An attack by North Korea would lead to retaliation, in which Russia could side with them.  Russia has been covertly selling arms to Syria, and Iran - through the company Rosboronprom.

3) Russia as of late has tried to create a people's republic in Latvia - such as when Latvian police this week investigated the creation of Latgale people's republic.  Such a move is parallel to what has happened in Ukraine.  If Putin is losing, this would be a trump card in his arsenal.