The Black Sea fleet losses are due to to a mixture of Ukraine’s home grown sea drones and UK/French cruise missiles. I don’t think this will lead to a nuclear attack by Putin.
In order to blunt this possibility, give Ukraine back the nuclear weapons they gave up in the 1990’s when the Kremlin (among others) promised they would respect Ukraine’s territorial integrity based on the 1991 borders. This will guarantee Putin will never use nuclear weapons on Ukraine.
