Like Valhelm you're falling into the same trap of treating Russia as kind of a democracy where the political leader's actions are shaped by the opinion of ordinary citizens in a sort-of bottom-up process. It's all true how you describe the views of ordinary Russians but, and that's the difference, they're being dictated from the top -- the Kremlin -- down to the ordinary Russians.
As an example, the concept of "Novorossiya" -- i.e. the annexation of larger swaths of Ukrainian territory and the creation of a new state -- had a support of 20-25% in Russia without a large propaganda drive. If Putin had made the decision to follow through on this concept, support for "Novorossiya" would've likely surged well, well above 50% for some of the same reasons -- historic land, always belonged to us anyway, yada yada yada.
Similarly, if Putin decides to change his behavior he'll rely on the Kremlin media to put an appropriate spin on it to sell it back to the ordinary Russians and they'll approve of it.
Pretty much. Russian popular support for things is whatever Putin decides it is.
There could be no sanctions in place and if Putin decided it would be beneficial to scapegoat the west, then that is what would happen. In fact that what was happening already before sanctions.