I believe I have an overall grasp of what you're saying, but I'm missing a step in the argument somewhere. On what basis did you conclude that the LDS does not have the mark of baptism, if not from prior consideration of their profession of a false faith? Same question with regard to discipline. Didn't you have to consider the LDS's lack of profession of the faith in order to arrive at the conclusion that their sacraments are not marks? I realize the profession of the faith is a mark, and even the singular mark. In that case, my only guess as to how you are rejecting the marks in their own right is that you must be using one mark (the profession of the faith) to overrule the others, which I guess makes some sense when you consider that the sacraments depend on the Word. Is my guess correct, or do you have some other explanation?
Fair questions. I don't think there is an "overruling." The fact is that the sacraments do not stand alone. They are significant ceremonies and therefore signify something. As such they are tied to the fundamentals of the faith. In the case of conversion some understanding of the Christian faith is required for baptism. In the case of infants the parents are required to believe the faith and undertake for their children to be raised in it. Hence the historic prominence of catechesis.