“I believe that use of tactical nuclear weapons in Ukraine is a real, ongoing possibility. “
What scenario?
Just for one off the top of my head: Ukraine aggressively attempts to take back Crimea and the seaport Sevastopol, with NATO weaponry and U.S. intelligence assistance. Or, Putin just get pissed off enough about the humiliation of losing ships and equipment from all military departments. I believe field staff would obey the command to load and fire tac nuke warheads at mainly military targets, at least within the general theater.