I agree with your second point completely on a moral basis. I do think it's unlikely the war ever ends without some territory ending up in the hands of Russia though, unfortunately.
The first point is a difficult one. Like I said above, he's never tried to push further into Georgia and has never tried to formalise the relationship with Transnistria, Abkhazia and South Ossetia. So I don't think it's a given that he'd continue to push further into Ukraine if some deal was agreed to end the war. It all depends on what his goals are, really. And who can really guess what it is that Putin actually wants?
My personal belief is that he wants to destabilise Ukraine in the same way he did/does in Georgia and Moldova by keeping, at least, an area of the country in permanent conflict. The country is going to have lost at the very least a decade even if the conflict ends today. Any agreement is likely to lead to internal conflicts that will set the country back even further. So, in many ways, it would be job done.
So I don't belief his goal is to take territory in the way that traditionally imperialist leaders do. Gaining Ukrainian territory isn't his goal, stifling the growth and development of the country is. So coming back to take more territory won't help him, however, say we get 5 years down the line and Ukraine may be able to join NATO. Well, that would be a great time to start another conflict over an area of Ukraine so that it doesn't happen.
But it's all guesswork. And if you're a leader of Moldova, Estonia, Latvia, Lituania or Poland, do you really want to take the chance that Putin doesn't actually want to expand further? If you're a leader of Ukraine, do you really want to take the chance that he doesn't come back in 5 years time when things start getting back on track? Especially if you know you're going to have tough internal battles to fight once the peace agreement is signed?
Honestly, I feel sorry for anyone who has to try and get a good resolution to this.