Remember lots of Russian tactics is pretending they can do a lot of bad stuff if people don’t do what they want. “Stop helping Ukraine or we will nuke you”.
Also USA has been pinning every single cyber attack on Russia/Iran/NK/China for several years, and I am personally very doubtful that western countries do not run ransomwares. In any case the result is that everyone thinks those countries do have the capability to do this.
Possibly, but I bet most of their nuclear stockpile hasn't been kept maintained and it wouldn't surprise me if parts of it had been stolen to be sold. This is why Putin threatens a nuclear attack, but doesn't do it as there's a good chance it would show how many duds they have (also setting off nukes would likely force a response from other countries).
Which their leadership never fails to mention when we (the EU) goes past some imaginary red line.
There are no red lines. There is only drone war and making Russia regret that they are attacking our allies.