That's a pretty old school realist view

I'd say great powers have fits of expansionism followed by periods of introspection or even isolationism. Europe has been in the introspection phase for some time, so I don't see any expansionist impulse there per se - the enlargement is almost complete and I don't see much support for including countries which are not clearly stably and culturally European (Ukraine, Turkey, etc.).
Russia has a dilemma, as you said. It certainly would like to re-assert more 'direct' forms of control over the ex-Soviet territories (especially the Caucasus), but its power is insufficient to do that. The West on one side and the Chinese on the other keep it in line. Still, should the West be pre-occupied by a major crisis in the Middle East, who knows what Putin would do. He's given us plenty of reasons to believe he's not beyond opportunistic aggression.
Possible, but it might backfire and destroy the regime. If you keep boasting about your military's ability to defend the country and then it fails miserably, your credibility in that respect is gone. Iranian opposition has been strengthening for quite some time, and such a failure might serve as a catalyst for the final confrontation with the regime. Or not, it's hard to say.
I think the purpose of the Iranian nuclear programme is multi-fold. Partly it's a prestige project, partly it is geared towards producing nuclear weapons, partly it's meant to support nuclear energy industry, partly it's a bargaining chip to be used in negotiations with the rest of the world.
As for Israel, it depends whether they believe a strike can succeed. Israel indeed has a deeply ingrained culture of military pre-emption, but it never was reckless in its execution.
The possibility of that is very remote. This isn't a Cold War environment.
See above. It's not entirely impossible, it just isn't very probable. If America goes medieval on Iran, Russia will loudly object, maybe sabre-rattle a bit in the Caucasus, but in the end it will back off as usual, knowing well it lacks the strength to actually force America to stop. It would be the same situation as when Russia crushed Georgia - the West loudly objected, but in the end, it knew it couldn't really do anything short of actually shooting at the Russians, which nobody dared to seriously contemplate.
---
Are you insane? Iranian population is, as another poster here affirmed, probably the most pro-Western in the Middle East, and you propose to exterminate it? Even by your logic, that would be a colossal stupidity (beside it being, you know, a genocide).
Western strategy in Iran should be that of containment and gradual subversion of the ruling regime. Basically the same strategy that ultimately led to the demise of Communism. I am sure there were plenty of morons in the West who at some point during the Cold War proposed to just kill "all of them Commies" and be done with it. Fortunately, their advice wasn't heeded.