Appreciate the response. On the second point, what prevents Russia from taking the land, pausing for a year or two to rearm, and then invading Ukraine again, or invading someone else? I really hate to make the comparison, because Putin isn't Hitler, but the UK and France thought ceding the Sudetenland to Hitler would placate him. It obviously did not. You suggest point four, but Russia's done nothing but bitch and moan about the encroachment of NATO as one of its reasons for starting to war to begin with. What security guarantee can be assured to Ukraine that isn't going to contradict one of Russia's reasons for invading to begin with? Ukraine and Russia signed an agreement after Russia stole Crimea from them. Didn't stop this war, mainly because Russia has no interest in stopping.
You're correct. If we hadn't supported Ukraine, the war would be over, and Ukraine would have ceased to exist as a state. It's never been about Russian-speakers in the Donbass. They sent their army to Kyiv, Kharkiv, and Mykolaiv for a clear reason. It's not going to be cheaper for us in the long run if Russia runs through Ukraine and sets its sights on Poland, Baltic states, and Moldova. Ukraine's army isn't purely defending Ukraine. It's a shield for the remainder of Europe to the west. The framing of the Maidan Revolution as a "US led coup" may as well be from Putin's mouth. The puppet in charge of Ukraine at the time wanted closer ties with Russia, a majority of Ukrainian people did not.