A- Crimea is Russia's red line. Its historical and military importance mean that Putin and its regime can't survive without it. Most of the time regimes aren't voted out and I doubt that Putin want to die anytime soon. A desperate Putin is a dangerous one both in terms of nukes and in terms of political decisions that he can take to avoid that (I'd come to that later). In both cases we would be in trouble. That include Ukraine btw.
B- The region is heavily fortified and most of its people are Pro Russian. So if Ukraine is determined to go in Crimea then this will end up in a proper bloodshed.
C- Ukraine is not fighting the war alone. If the West decide to pull out its military help then it would be game over in a couple of months. There's plenty of leverage in that
D- Russia is sinking deeper and deeper in China's pockets which is bad news for the West. Russia on its own is a regional power armed with nukes. A China-Russia partnership is terrifying. The former have the men and the weapons while the latter have the resources. Add Taiwan (and its precious semiconductors) and the three can easily go toe to toe with the US and the West. Such alliance is bad news for Ukraine as well especially if China start supplying Russia with arms. We need a relatively strong Russia as that means an independent Russia who still believe it can go solo against the world thus not needing the 'inferior' Chinese (that's the typical Russian mentality and not my opinion).
E- Semi conductors makes the world tick. You'll find them from the fridge you have at home right to the F35 the US utilise to control the air. Over 60% of semiconductors are done in Taiwan under huge trading secret. Thus there no way the US will allow China to invade Taiwan and if it means throwing Ukraine under the bridge to focus on Taiwan then so be it. Its within Ukraine's interest to end this war fast.
F- Russia can throw far more men into the war then Ukraine can. It can also bombard Ukraine from Russia knowing that no one is stupid enough to strike Russia hard in its own territory. This create an environment were there's a never ending war which is bad news for Ukraine. The country is in a mess, it needs heavily investment and it needs to move on. Support from the West will one day weaken or end as well. Time is indeed in Russia's side
G- Wars often end around the negotiation table especially one were its impossible to invade the invader for obvious reasons. Negotiations mean that everyone wins and lose a little.
I believe that the deal I suggested is fair to everyone. Ukraine gets NATO protection and the prosperity guaranteed by EU membership, Russia gets the political win it needs to leave the conflict with dignity and the people in Ukraine (including those in Crimea) will live in peace. Don't take me wrong I'd love to see Putin's head on a spike. However that is unlikely to happen and the consequences to that would probably be far worse then anyone in the West would want, Ukraine included.
A - their red line shifts constantly. When they annexed the 4 Ukrainian regions, they also told the west that they will regard them as Russian territory and that means defend them with any means, nuclear included. Ukraine attacked 2 of them and pushed them back, liberated Kherson. Did Putin press the red button? No, he did not. Fearing and talking constantly about Russia's red lines only helps their fear agenda. Mostly useful idiots talk today about Russia's red lines. By the way, the western red line is far more dangerous than Russia's and I never see them talking about it.
B - When the Crimean bridge exploded, there was miles of traffic jam because of people leaving the peninsula. It's safe to say, that if Ukranian forces would stand before Crimea's border, most of the Russian's would flee. Especially those, who settled there after 2014. So bloodshed is a very unlikely scenario.
C - The west will never pull out of this war, because it's no longer only Russia against Ukraine, but an authoritarian regime against western democracy. We defend ourselves by supporting Ukraine, so we will defend ourselves as long as it is necessary and Putin is no longer a threat.
D - A China - Russia partnership is long established and far from being terrifying. Nato will always be way stronger as long as the U.S continues to lead Nato and China uses Russia as a ressource colony. There is no real partnership between them other than to annoy the west. Also if your partnership is only based on a common enemy, it is shit to begin with.
E - one has nothing to do with the other. First of all, China still needs many years to build up their navy. Second of all, U.S is giving Ukraine something like 5% of their annual military budget and they don't use their navy to support Ukraine. The U.S would absolutely have no problem to support Taiwan while giving Ukraine 5% of their budget to keep Russia in line. Also no one on our, the western side, will throw someone under the bus. A very strange thought.
F - Russia can only theoretically throw in more men. In reality, it's probably even fewer. Ukraine is the one who was attacked, so most of their men are willing to fight for their country and freedom. While Putin needs to irradiate russians to order them to die in human wave attacks. They already ran out of prisoners and the first mobilisation wave wasn't as smooth as he would have liked. With every new wave, it will get harder and harder for him to find more "volunteers" and willing men to die for his imperialistic ambitions, while keeping the public quiet at the same time. They also have internet and see those gigantic cemeteries for their soldiers. And the sanctions are hitting their economy hard. The longer this goes on, the fewer funds Russia will have to finance this war. Their funds will run out way sooner than those of the west. They can't win a money war against the west, it's impossible. So no, the time is definetly not on Russia's side.
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Many things you wrote are said in pro Russian channels. Talking about red lines, the narrative of the strong Russia and the weak west, that has to end his support soon is only used by useful idiots. I really hope you're not one of them.
Doubt it though.