Appreciate the detailed response, and it seems we are very broadly on the same page.
Assuming no further military push from the West -- do you think the Russian side would acquiesce to some form of "Cease fire along current lines, but no legal recognition of the territorial claims, and no lifting of sanctions or arrest warrants, and no return of seized foreign assets"?
(That's very far from my own ideal outcome, but I'm just trying to get sense of how you see the situation).
It's hard to say. It would be essentially the same thing they already did back in 2015, so there's precedent. But back then it happened IMO because they didn't think they were sufficiently prepared in economic and military terms to openly wage war, so Russia took as much as it could with the "northern wind" (the euphemism separatist forces used to refer to direct Russian involvement in combat) and then took a break to prepare for the real deal.
So I think now they would do it if they believe that taking another break would benefit them more than it benefits Ukraine. But, again, looking at post-2015 developments, it's not clear to me why they'd think that. The reason why their advance in the east was so much slower than elsewhere is that Ukraine had a massive effort to build fortifications and infrastructure around them under Poroshenko. It's why Ukraine could hold Avdiivka for so long despite it being less than 10 miles away from Donetsk, and it's partly why Russian losses are so high. Russia has managed to punch through that line in several places in this past year despite those high costs, but if they stop the advance now, that kinda defeats the purpose of that. And meanwhile if Ukraine could get some respite, they would surely spend a lot more resources on another defensive line along the new border, probably with significant Western assistance this time, as well (since "defensive" military aid generally enjoys higher popular support, countries like Germany might be more willing to do that even if they aren't willing to send more tanks and missiles). As well as building new munition factories etc, likely also with Western defense companies involved. It would also mean the return of millions of Ukrainian refugees, reinvigorating their economy.
This all assumes that Russia wants to take as much Ukrainian territory as they can get away with, in the long term. But, given that the war literally started with them trying to capture Kyiv, I think it is a safe assumption. If they gave up on that goal since then, they wouldn't be pushing so hard now despite the losses.