At what point though is it incumbent upon the person with the "bad (cultural) habit" to change them, ethically? When it leads to harm? When should a cultural habit that leads to possible harm be excused? — schopenhauer1

You seem to be conflating the questions of self-correction and other-correction, which I want to keep distinct. I already answered your first question: "when it is self-consciously recognized to be a bad habit and the necessary resources to make a change are available." What is bad and what is harmful are not identical notionally, but if someone thinks that only harm is bad then they will only self-consciously recognize something to be a bad habit if it is harmful.

(We can only self-excuse when we lack the available resources to change, for the very fact that we are considering excusing shows that we already see the habit or action to be bad.)

Self-recognizing as bad habit seems to be vague then. You are stating a truism rather than a normative course of action.