And if Ukraine keeps on resisting Russia and attacking it again and again (particularly continuing the terror attacks against apartment buildings in Crimea and Russia), then Russia will roll through Odessa and take more and more until there is no Ukraine left.
Exactly. I think it was a good move from Russia to declare the demilitarization of Ukraine as one of the main goals because it allows you to stretch your territorial claims depending on the military-political situation.
I think Russia's openness to negoatiations is genuine. I also think that Russia wouldn't want to take Odessa if the goal of demilitarozation would be achieved at the negotiation table. Whatever keeps NATO from turning the Black Sea into its inner lake would be acceptable to Russia. Partly because of the cost sink issue touched upon be Samseau. But only partly. Ukraine to Russia is not Afghanistan/Iraq to US, you don't measure such things as history/roots/collective memory in shekels.
which is take over Ukraine (a massive cost sink for them)
On the other hand, Russia takes following into account.
1. The Minsk agreements were a betrayal.
2. The "peace talks" in Istanbul were a betrayal.
3. AFU's military strategy (lack thereof) consisting of holding every inch of the territory and terrorizing Donbass forces Russia to expand her territorial claims.
It means that the window for "peace talks" is narrowing and the options for Ukraine are shrinking.
Right now I see only one scenario in which Ukraine can continue to exist with more than 50% of its 1991 bordes - coup d'etat and pro-Russian junta signs everything Russia wants it to sign. But this could potentially trigger a NATO invasion. Not very likely, but still probable.