Dear god, where do I even start? Everything you just said is laughably wrong.
First, if you think military alliances prevent wars, I suggest reviewing World War I history. Also, I have no idea where you've gotten this idea that the world is more peaceful now than it was 70 years ago. Do you have any idea how many armed conflicts the US alone is involved in? The US has taken over meddling in the affairs of African countries now that the Soviet Union isn't around to do it anymore. Neither is justified...
...and I'm tired of tankies pretending that it is.
Next, no, NATO expansion was definitely the provocation. The democratically-elected government of Ukraine (which was allied with Russia) was overthrown by a NATO-backed coup in 2014. The oblasts of Donetsk, Lugansk, and Crimea refused to accept this, and seceded. Putin ordered the occupation of Crimea, but Ukraine invaded Donetsk and Lugansk.
Pro-NATO shills in Ukraine call this the "Euromaidan revolution," but everyone else calls it the "Euromaidan coup." Does it justify Putin's actions? No, absolutely not, two wrongs don't make a right. But my question to you is this: why does Ukraine deserve self-determination, but Donetsk and Lugansk don't?
Also, Russia hasn't lost half its army (just half its tanks), and Ukraine isn't winning. Ukrainians don't even want to fight anymore, and NATO is calling them cowards for it.
Putin doesn't even want more territory. It's an administrative nightmare to expand Russia, and Russia has plenty of natural resources, just not a whole lot of high-tech manufacturing, hence the need for trade, which segues perfectly to my next point. Putin only wants a direct land connection to Crimea because without it, Russia has no ice-free deepwater ports. This wasn't an issue when Ukraine and Russia were allies, but as you can see, alliances aren't forever, thus nations need to be as self-sufficient as possible. Putin knows this, I know this, but the oligarchs don't care, and thanks to systemic apathy brought on by corruption and government red tape, change is going to have to come from the top. We can't rely on West Taiwan forever.
I'm saying that the number of international wars has decreased, ie, the number of times one country has attacked another country is less in the last 70 years than, say, from 1800 to 1950. I think this is due to increased military ally networks in the world since WWI.
Ukraine is winning for as long as Putin doesn't succeed. As long as Putin doesn't forcibly take over the government of Ukraine, they are winning. If they're able to limit the number of towns the Russian army will bomb to the ground and civilians they murder, they're winning. Again, the Russian army can stop their invasion at any time to save both the lives of Ukrainians and Russians.
I honestly don't know much about this region, but the people of Donetsk and Lugansk want to succeed from Ukraine then I would support that. With nearly no knowledge of the history, if Ukraine invaded Donetsk and Lugansk and took away their rights that's clearly wrong. I don't see how the Russian army bombing their cities into dust and murdering the citizens actually helps the people of those regions now though.
Your opinion that Putin just wants a land bridge to Crimea definitely sounds plausible. I haven't heard that opinion before so thanks for sharing that. Personally I'm not sure if trying to march on Kyiv, turning cities to dust and murdering civilians is better than developing ports in places like Sochi, but again, I really don't know much about any of this so I'm sure there are many factors I'm not understanding.