The little I know -“In other threads in the CR, the discussions about smoking included the overwhelming majority of rabbonim and poskim who stated unequivocally that smoking (yes, even the single cigarette) is a clear issur mid’oraysa.”
While I agree with the rest of your post -your statement of “even the single cigarette) is a clear issur mid’oraysa” -I totally disagree with. When you make something totally Ossur, when it’s not, then it is much harder for people to comply. One pack a year is clearly not dangerous and probably even more than that. People tune out the message when it’s over the cliff.