Just to reassure you. If you try the nagging appoach and he cares for you, you will NOT become his ex, but rather you will find him smoking less often. I think it is very healthy in a relationship to voice your concern if something is bothering you (Noone should settle for something they find repulsive, it can lead to further disenchantment in the relationship).
If you become an ex for voicing your concern about his bad habbit, then you would become his ex for voicing your concern for just about anything
