The difference is that with moral behavior a person does not pay as heavy a personal price as with being observant of the commandments. Beyond that, if you do not keep the commandments, no harm is caused to another person (or at least it is not clear what harm is being caused here); rather, he just fails to uphold the truth, unlike moral behavior, which is indeed connected to that issue.

That is a quantitative distinction. The fundamental question is whether one can justify conduct because it is right, even if it is not convenient and does not bring me personal benefit, or not. My answer is yes, and the proof is from morality. How far does this go, and how high a price are you willing to pay? That depends on the degree of your confidence in the correctness of the system in question, and also on the (spiritual) harm in not observing it—which for some reason you assume does not exist.