>

Exactly (although I wouldn't say Russia's victory without western support is assured). That's why it's important to ramp up arms now. Sending a few tanks isn't enough, but breaking the "taboo" on sending tanks is a pretty big deal, it will be much easier for more to follow. 
The good thing is that the West doesn't really need to try particularly hard, or make many sacrifices to continue their support at a level that exceeds Russian economic capacity, so it's not like there is much pressure to turn off the money faucet from within Western countries. 

Russia will just drag this out for years

They'll certainly try. But there's nothing like an unambiguous bad guy to bring people together. I'd bet my entire life savings that the Russian state collapses before the US and EU stop supplying Ukraine. Even if the general public loses focus, it is a great military investment. <2% of the annual military budget to counter one of our most irritating geopolitical adversaries. Even with the rise of right wing populism in Western countries, I don't see support faltering. 
But supplying Ukraine with more and faster should still be the goal since it would help Putin or his successor reach that inevitable conclusion faster.
India is making a killing here.  Buy low, sell high. >

Everyone wins. 
US and European politicians get to claim they're cutting out Russian gas without dealing with massive price spikes
Russia continues to get funding, at a lower level but still a lot of money
And India as the intermediary makes a healthy profit >

Ukrainians don't win. >

Sure they do. Russian fossil fuels are selling for pennies on the dollar, so sanctions have significantly cut into Russia's profit and thus their ability to fund the war. 
And keeping fossil fuel prices in a reasonable range alleviates pressure on NATO and other pro-ukrainian countries. This makes it easier to continue supporting the war. The more isolationist wings of the various political parties in NATO and related counties would be up in arms if fuel prices dramatically shot up. 
Russia isn't under embargo. Sanctions aren't meant to prevent Russia from getting stuff or selling stuff, they are meant to cripple the Russian economy, not kill it outright.  There probably is an argument to a full embargo, but it's probably more important to not alienate India, China, and other non-western countries. They aren't really helping Russia in any meaningful way. We don't want to change that. 
As long as India pays below market rate for Russian oil, it's fine. The Ukrainians need more tanks, more rockets, more AA (like F-16 or Patriot), and long range strike capability. They don't need India to stop buying oil. 
Russia can't win a war of attrition against Ukraine if the West backs Ukraine. We need to show Ukraine and Russia that the US, EU, and other are in for the long haul and will give whatever is necessary for however long it takes. 
31 Abrams isn't sufficient. Let's stop pussyfooting around and give them more. For every tank they lose, let's give them two more. >

Russia's win condition hinges on getting the west to give up on Ukraine.  If they can manage that, their victory will soon follow.  The Ukrainians themselves will fight to the end; it's hard to see them ever giving in (even if they have to fight using something like IEDs) when the other side constantly engages in genocidal rhetoric.
Unfortunately it's also hard to see Ukraine winning in any meaningful way.  Russia will just drag this out for years until the west inevitably loses focus.