A new normative theory and a PhD thesis It is not only humans that are morally relevant. Any kind of person, be they human or not, surely matters just as much. It is not our humanity that makes us matter, it is our personhood.
What do you mean "reach beyond"? If you mean find out if our perceptions are actually reliable and actually represent the external world, then they can't. We are doomed to forever experience only our perceptions, and never the reality beyond them. But whether such a reality exists and, if so, what that world is like is a matter of objective fact. The answer to those questions are true regardless of whether people can ever know them. I suppose what I am getting at here is that there is a difference between something objectively existing and/or being true, and whether we can know it to be true and, further, whether we can know it to be true in a way you would consider "objective". Or, to put it another way, there is a difference between epistemology and ontology.
I do not fail to realize what subjective means but, using your definition, I do not remotely except that what we perceive dictates what is true. There may be things that we, or someone, cannot perceive in any way but the way we, or they, do, but that may not be objectively true.
It should have priority because if morality is the way in which persons ought to be or act, then it must be able to apply to all potential persons, not just humans. And I suspect these other human potentialities (assuming you mean any of the things virtue ethicists generally care about) you are talking about are not necessarily shared by other possible persons.
I would not say you "ought to do whatever you want". I would say you ought to be free to make your own choices. If a person decides to do something they don't particularly want to do, there is nothing wrong with that. The wrong comes in the violation of their ability to make and understand choices. As for how I establish this is the case, it goes back to freedom (by which I mean the ability to make and understand one's choices) being the best candidate for moral value. Which goes back to my assumption that morality is the way in which persons ought to be or act.