Is it permissible for one afflicted with smoking, who has been unable to quit, to continue leading prayers (Imamah) and delivering sermons (Khatabah), given his fear that he might be among those by whom the Fire is kindled on the Day of Resurrection?

We advise you not to abandon preaching and reminding people. It is not a condition for a preacher to be free of errors. As long as you do that and convey what you know of Allah's religion, striving to adhere to the Sunnah, and keen on sincerity, then you are not among those with whom the Fire will be fueled on the Day of Judgment. If you find someone more knowledgeable than you, present them, and continue to adhere to the Sunnah and be a good example. As for smoking, scholars have issued fatwas prohibiting it due to its harm. We advise you to strive against yourself to repent from it, seeking Allah's help, and if there is no other way, then gradually. You can consult the counseling section for more methods to quit it.