My real question is not whether it would achieve anything meaningful, but what would be the side effects of such a strike on allies in the region.

I don't have a remotely decent mental model of fallout etc from modern nuclear weapons - my assumptions are they're still toxic enough to be a bloody terrible idea anywhere near someone you like.

You're assuming the current president operates on rationale. He simply would love to be the guy who uses a tactical nuke.

The shock and awe from a nuclear strike is unmatched

Wouldn't*