The problem with "The only action that will save Europe is an unconditional revocation of its self-destructive sanctions and a peace agreement in Ukraine on Russia’s terms" is that it is back to front. The truth is more like "The only action that will save Russia is an unconditional revocation of its self-destructive invasion and a peace agreement in Ukraine on Ukraine's terms."
I think your conclusion is based on incorrect assumptions:
1) We are well on the way to complete defeat for Russia, so this assumption is false.
2) Ukraine and Russia have no common ground for a peace agreement, so this assumption is correct for now.
3) Military defeat in the war will result in Vladimir Putin being removed from power.
Putin's removal would be the trigger for a peace treaty, as Putin is incapable of accepting his own military failures.
As for your faith in the Russian economy, here are some links for you: