I think you are spot on.
S300 are anti-aircraft missiles. Converting them for surface-to-surface use is very inaccurate. So they are not targeting specific civilian objects, they just don't care. If they aim them roughly at civilian areas, it can still be a war crime, and it is tactically and strategically mostly useless.
I wouldn’t be surprised if
Neither would I. Just saying that "smoking at the workplace" alone won't suffice. Unlike in, say, a ~~fireworks~~ munitions factory.
The way I see it: it is either mostly ineffective (against infrastructure) or a war crime if used again against people (civilians or combatants).
Can transformer cooling oil form flammable vapour? Maybe, I guess, if it's hot enough, but I'm not sure. But when the transformer gets hot and explodes it may cause an oil spray fine enough to create a fireball, which may look similar. The first stage of a "proper" BLEVE is normally the "expanding vapor" cloud, which is visible as such, before it has mixed with air sufficiently (and/or reaches an ignition source) to burn and form the fireball. Then again, in smaller ones, and in the dark, the vapour cloud may be so short-lived that it cannot be seen.
Not sure this has been the official "explanation" this time, but looking at it from a technical side, there isn't normally anything in a transformer flammable enough to be ignited by a cigarette, even if you could drop it directly into the cooling oil (which you can't: they are normally sealed). My understanding is that you need a sustained arc over several minutes of "normal" electric current, or several lightning strikes to heat up the oil enough to catch fire. That requires some major fault. I guess a suitable type of warhead could cause it eventually, but not immediately.
What are we looking at? Incendiary cluster munitions?
Yes, or other light aircraft. Not military. But what is or was in the building is anyone's guess.
I heard about 60 from Jordan. Have to check my sources.
That thing still looks like a combat robot from a science fiction movie. Especially the muzzle devices look so silly. I know they are important as they measure the actual muzzle velocity, which helps to make it as accurate as it is, but still: 
They need more Gepards! They can do it with fewer shots, I guess. But even though slow and low, hitting those things with manually tracked FlaK is no small feat. Well done!
Oh no, another red line! How many were there now?
Normally, the Russian air defense should deal with Tomahawks easily (they've had decades to prepare: Tomahawks are nuclear-capable, so it was a top priority to develop the look-down shoot-down capabilities of the MiG-31 and others), but the way it's been going recently I would give it a substantial chance of getting through to Alabuga.
Is this a translation error? Did the S300 really hit two Ukrainian S300 air defence missiles? That would be an unexpected operational success. I assume a "with" is missing: "the Russians hit with 2 missiles ..."