Right, which is the problem… When you are trying to establish if something exists you don’t assume that it’s already true.
You have actually presented zero argument that bodily autonomy is a right, so we really have no basis for assuming it is. Even if you try to make personal rights arguments this can be refuted as a failed descriptivist argument. Are medical decisions being left to the individual due to a inherent right to bodily control, or the fact that people who are directly affected by a decision chose better outcomes? The bodily autonomy argument does not account for why we think it is good to deny people the ability to make poor medical decisions (i.e children, the mentally handicapped, ignorant people, or in the case of prescriptions anyone without sufficient knowledge). The latter argument does.
“A more moral person”
I think I already answered the question. Both individuals are acting morally by saving others, although saving more people is a better outcome.
“How do you determine when it’s a moral principle and a psychological preference”
This is a difficult question. Some cases are apparently obvious, like saving attractive people. In general the problem is searching for the answer that best satisfies our intuitions about morality and reasoning. The primary argument for when a feeling is insufficient, is if the basis for it is too complex. The purpose of a moral system is to provide a set of rules and methodology to determine if an action is morally good or not (otherwise we would just rely on spontaneous feelings, with all the problems of individualistic moral relativism), it does not make sense to rely on feelings about a morally complex action to override a more fundamental principle. At some point you have to say that your feelings about something are not morally relevant.