Nuclear and military threats will never end no matter what we do because there is no world government to stop them.

Wrong. Even without world government, other governments can punish those which make threats (economically, politically etc.) to the point of making threats a bad deal for those that make them. And not dishing out such punishment (i.e. letting things slide for Putin) will only make threats more common. Putin started a war in 2022 because he thought he will get away with it again, and luckily this didn't happen.

No matter who wins in a war, one side provides an example of military threats working and another side provides an example of military threats failing. 

Wrong. This is symmetrism at its finest. Ukraine is not making any threats, it's the same case as with a person who got robbed and wants their stuff back  - they're not making threats either. The only one making threats here for many years now is Putin and his mafia-state. There is a fundamental difference between a country not violating the borders of its neighbours (Ukraine) and a bully (Russia) who stirs up problems. The only blame lies squarely on Putin and his gangsters.

I never made that assumption. I do say there could be a peace treaty. 

But I made that assumption, because your assumption of Putin respecting any peace treaty ever again is plain wrong. That's not what the guy does nor will do at this point. He played his hand and its either military defeat or victory, now or in the future, as long as he stays in power.

remove tension of areas having de facto seceded

Seceded with what? Opinion polls? There was no secession to speak of before Putin rolled in with his military disguised as local rebels: https://en.wikipedia.org/wiki/Annexation_of_Crimea_by_the_Russian_Federation

and Putin wanted (among many other things) to ensure the long term security of Crimea and DPR/LPR. 

Oh, poor Putin :( He only wanted to play nice :( He could have just not started the war in 2014. Or 2022. Or 2008 with Georgia. 

So I don't know why you'd bother to say this. 

Because you literally back up your main argument with a link to the post, and the linked fragment starts with "Crimea's 2014 status referendum provides one indicator of public opinion." - no it does not, now  by your own admission. However, the impression your writing makes is that the referendum is a solid data point. Again - it is not. Nor are the earlier polls. "Will of the people" in such important matters as statehood cannot be simply inferred from polls with a sample size of 1000-2000. Also, analysing many polls side-by-side shows, that their results are at best inconclusive.

If there ever was a solid case for secession there were plenty of avenues to pursue it, without Russia starting wars in 2014 and 2022. They knew there was not, hence the wars. And now that they did start them, they blew it forever. Any discussions now should be made remembering, that a terrorist state (Russia) attacked Ukraine in an act of unjust, total war - and this overrides any concern for any Russian interests and claims they might have ever had. Putin just ousted himself from being considered a civilized leader and cannot be treated as such, nor anyone can give any credence to his claims or claims of his supporters.

@kbog
The first and the greatest reason for a possibility of military and nuclear escalation is Putin and his dictatorship, not Ukraine, NATO or EU. Conceding anything to Putin and his collaborators at this point will only give them reasons to believe their tactics work and so, nuclear and military threats will never end. All the relevant arguments - political, historical, humanitarian, legal etc. are on the Ukrainian side. (In your own words: "The idea of Ukrainian sovereignty over Crimea is supported by international law"). With or without Crimea Putin will try to interfere and destroy Ukraine as long as he is in power, so you are wrong with the assumption that Putin will stop with Crimea in his hands (he very clearly didn't thus far) and Ukraine will be free of burden. Any utility calculations beyond point are futile, because these arguments give a good enough heuristic to follow and they already point to the highest value decisions.

Also, the main argument, that people living in Crimea want to join Russian Federation is just plain and simply, wrong. The very source you point to in 2021 forum post (https://en.wikipedia.org/wiki/2014_Crimean_status_referendum) points out a number of methodological issues with the referendum and also - in plain terms - it was done while the area was controlled by the Russian military, so exactly zero faith should be put into these results. Also, before the referendum there were a number of factors influencing the earlier poll results, so that we should not call these "the will of the people".

Therefore, the entirety of your argument is just plain wrong, sorry. Calling anybody to spread a message contrarian to very obvious points I've made above is just bad for everyone - EA, Ukraine, Russia, Europe etc. etc. It only benefits Putin and his lackeys.