Putin cannot accept a failed invasion
He would lose face and his power structure would collapse. He will escalate regardless of the losses they suffer
Agreed. I don't see "the win" for him in any event. Russian troops will eventually have to go back to Russia, and they are not happy campers with happy tales to share.
Putin's best case scenario seems to be he "keeps" the two Donbass "oblasts." In 1991, the local populations voted to remain Russia, at least in terms of not being governed centrally from Kiev (I'm too old for new spellings). But "polls" past then are uncertain at best. But nowhere else in Ukraine does Russia get any warm props. Even in Crimea, although russia's succeeded in getting a lot on non-Russiafrienly people to leave Crimea (or else).
But eventually, embargos on Russian carbon will reduce the price Russia can get, because the carbon won't be traded in a global market, ie Putin will continue having to discount the carbon. That's not all good for us, btw, since he'll be paid in roubles or renminbi.
Even assuming he can sell a stalemate in Donbass to Russians as a win, the Ukrainians will continue attacking Russian soldiers in any land occupied outside the two Donbass. The Russians might find a "friendly" occupied population in the Donbass Republics, and that might make it harder for Ukrainians to kill them there, but that's not the situation anywhere else with the possible exception of Crimea. But even there, Russia is not popular in territory connecting Crimea to Donbass. That would remain pretty much a killing ground, because Russians would be sandwiched between the Ukrainians and the sea, ie a static target.
That's why BIDEN'S GAFFE was inexcusable. It's hard for me to see anything PUtin can accept other than continue to kill civilians.