It's not a "moment in time" calculation. Russia will make an assessment not just of what the costs are today, but the future costs throughout time. As is frequently the case, the invading country presumes that it will be able to eventually defeat the opposing forces conclusively. If they fail to defeat the opposing forces for a long enough period of time, that presumption is no longer valid - and they have to reassess the costs and benefits. Russia is still in the "we can still beat Ukraine" phase of assessment. That will eventually change, if they are unable to beat Ukraine for while longer.

Certainly. But you're not taking into account your own analysis of the situation.
Thus far, despite some sanctions, Putin has been able to fund his war by selling oil to China and India. According to you, it's not possible for the West to make a unified front via sanctions in such a way to impose enough costs on China/India to lessen that flow. So there's...nothing...that's going to change the economic or strategic calculus as Putin doesn't care how many soldiers he throws away.

It's not useless. It's just not made for this particular purpose.

So if it can't defend itself without being held hostage by one of its least important members (note that Hungary is also in China's pocket) then it's useless.

It's an economic union, not a foreign policy or military union.

An economic union that can't act in unison against what it determines as an existential threat. Or are you going to start arguing that the Europeans don't view the Russians as an existential threat?