I don't disagree with your main premise but Russia's battlefield nukes probably still work. Those are fusion weapons that require little maintenance, just a couple of sub-critical-sized pieces of fissible material that need to be slammed together to go critical (boom). For the artillery shell nukes leftover from the Sovs, the explosives *might* be past their shelf life, but who knows? Long shelf life explosives were developed in the West in the decade before the USSR collapsed. It doesn't seem they switched their artillery shells in general to this but I would hesitate to make the same prediction about the nuclear ones (different manufacturing facility, different priorities).
The theories about Russian nukes not working due to no maintenance is about their *fusion* nukes as an element in the weapon (tritum) degrades over time and needs replacing. But those weapons are designed to use a fission reaction to initiate the fusion reaction. That means they're still fission weapons going on overhead - and can still ruin your day.
All that said, I don't think they'll pull the trigger / push the button as they *know* the Western arsenals are fully functional and I'm pretty sure Putin has been informed that the West would be targeting him in particular - and I don't think he wants to commit suicide.