If Russia could bomb kyiv more than they have, they already would have. They literally dont have the strength.
Nukes would likely drag Europeans into the war formally, which Russia cant handle. They dont have resilience, and their oligarchs dont want a nuclear war any more than we do. At the end of the day they are cowards; once their actual livlihood is at stake they will cut and run to save whats left.
Russias only actual card is political division. Biden effectively gambled the US would be more politically resilient than it actually is, and appears to have been wrong. Putin gambled he could manipulate enough in the US to turn the tide.
Now that Trump has exposed it, imo it actually increases the risk because now one warning Nuke can maybe whip his followers into line.
Ultimately today Z played new cards. He saw the writing on the wall, knowing agreeing to Trumps current deal would likely be the (eventual) end of his country. So he appealed to the US voter. This bypasses Trump so it was never going to end well. Now the next phase plays out. Trump tries to discredit z; if he wins its over. If he loses we go back to the Biden plan, rebranded as the Trump plan one way or another.
Strategic victory for Putin in the meantime. JD isnt cut out for the big stage is my main take away.