Why would Putin contaminate seafood and shipping lanes, along with letting fallout flow eastward into Russia? I do not see this escalation as being likely. It’s possible, but it hurts Russia as much, or more.
Maybe Russia sets off one in the Arctic, but, again, what is gained? He could just as well use chemical weapons, and those have a much more isolated effect.
“Why would Putin contaminate seafood and shipping lanes, along with letting fallout flow eastward into Russia? “
It would be a real=life example of EMP effects on modern electronics, too.
A tactical nuke over the open water would create essentially zero fallout, nor EMP effects at any distance.