If Russia manages to occupy Ukraine through repressions then wouldn't this invite Chechnya 2.0, but with 30x the people? Can the Russian state even survive something like that?

Yes it would, but those able to would eventually leave the country and those peope left will tire out, run out of money and will. I don't know what Putin thinks at this stage, I think he desperately needs a win to restore some credibility back home.

I'd say he's going to invade Moldova in the next few days (once Odessa is taken) and make a big show of how easily they took it to restore morale, and very soon after they're going to plunge in Ukraine's back and make a big push for Kyiev.

I think they might abandon installing a puppet government, but in that case they will bring devastation to Ukraine and keep the whole Black Sea coast, and just let Ucraine fester.

That's insightful and cynic. Possibly right too.

But why "modern tyranny"? Wars like that are not a novelty... or is it about taking civilians as hostages?

Because with modern technology oppression is a lot more efficient than before. Not says that it was not in thr past.