I'm going to focus on this, because I think it's the core of where we're disagreeing or dancing around each other:
I think I have a better way to cut to the chase of this. If you ask me the question, "What ought I to do?" I am going to answer with some variation on, "It depends on what you want." This is all inclusive: It depends on what you want to happen; it depends on what you want to gain; it depends on what you want to achieve; it depends on what you want to experience; it depends on what you want to feel; it depends on what you want the outcomes of your actions to lead to.
Do you want to be happy? Then list XYZ are the things the sufficiently-informed guru/spiritual advisor/life coach can objectively tell you to do to become happy. They are the answer to, "What ought I to do?" if you want to be happy.
Do you want to be a good person? Then (in D&D or a system that uses a similar alignment grid) you ought to do those things which the good alignment says good people do.
It is not presuming the conclusion to say, "You ought to do what the alignment you aspire to requires." If you asked "What is the moral thing to do?" of somebody who knows what alignment you aspire to, he will (assuming he is both correct and honest) tell you what the alignment to which you aspire says one should do in the situation you find yourself in. Because this hypothetical involves an objective alignment system, there is an objectively correct answer provided by each alignment. ("It doesn't matter; this is an amoral question" is also a valid answer, but I am neglecting it for now; we are assuming we have correctly identified our "what should I do?" questions as pertaining to the objective moral alignment system.)
To reiterate: The answer, without making any assumptions about the asker at all, to the question, "What ought I to do?" - regardless of whether morality is objective or subjective - will always be, "It depends on what you want."