You can't rely on either of those assurances. Sure, Stanislav Petrov famously disobeyed Soviet orders and in the process averted a nuclear launch in response to a false alarm. In 1983.

One lesson Putin would have taken from this is that all officers in the nuke launch chain must be subjected to loyalty tests, where they are made to believe that a launch drill is real. This will weed out those future Petrovs that you are assuming will be present.

Until recently we had mutual weapons inspections via START treaties that allowed us to confirm in person that their nuclear arsenal is in fact not mostly useless. Those weapons do exist and are operational, and unless you are a complete idiot doing whatever it takes to ensure they remain so as much as possible will be the priority of any leader.