Russia just threatened and attacked European energy and security, European troops (not NATO) should move into Ukraine and start killing Russians in large numbers quickly, shock and awe. Go all in with Ukraine on a bilateral basis starting with Poland. Stated objective to liberate all of Ukraine, or destroy the Russian army, whichever comes first. If they want it to end, then end it, if the Russians wanna start tossing nukes, they will commit suicide over Crimea. One way or another they are gone, in 24 hours or leave what equipment they can't get out of the country, if not, they will be driven out of the place with maximum losses. Freeze or fight, it's up to them, Ukraine has all the NG and oil the Europeans would need for the foreseeable future.
A better option might be the American plan to strangle the fuckers while the Europeans freeze a bit this winter and we try to get the poor folks feed as best we can. Bleed them white and finish them off in Ukraine, if the leadership can't withdraw them for political reasons back home. Don't do anything that will give Vlad an excuse to mobilize manpower or declare war. Right now he can't withdraw and he is hamstrung in reinforcing them because of manpower issues and a host of other systemic issues in his army.
The stalemate won't last forever, Russia grows weaker and Ukraine grows stronger with outside help and a large pool of volunteers. They had a 200K+ regular army and an over 400K reserve with military training and combat experience over 8 years of constant low level warfare in the east. Since the war began they have been constantly training and equipping new recruits with allied help. If they lost 100 troops a day on average killed over 100 days of war, that's 10,000 troops and say about 20,000 were disabled, or out of the fight with serious wounds, that's 30,000 people gone for good.
The Ukrainians won't run out of manpower or morale, they are tired, but people have fought wars for years and if it's an existential fight for a nation and culture it will go to the point of extermination. There is no other end for this war other than Russian defeat and being driven from Ukraine and even then it will not end, but will move on to other fronts. If Ukraine gains Russia's oil and gas markets, they will be come very rich in a hurry and if they are rich, they will be militarily very strong, considering their recent history.
They won't want Belarus on their border with the current government and neither will the Poles or Baltic states. Forget Kaliningrad, he better worry about Belarus once Ukraine gains the upper hand in this war. Trouble in Belarus with the Ukrainians supporting a new government would see Russians evacuated from all of Ukraine and sent there. If he loses Belarus, forget Kaliningrad and the Baltic in general, he will also have Europe as Moscow's neighbor. Belarus has undeveloped gas under it and the pipelines that carried Russian gas run right over those fields too.