You have tried to gloss over what matters most, if anything matters at all. What does it mean to value? But first, what are you quantifying over when you quantify over harm vs. well being? If you are being consistent with your metaphysical commitments, aren't you simply marking the difference between a collection of matter with a contiguous boundary in time and space that stays intact vs. a collection of matter that doesn't? What is a human other than a collection of matter? Sure, we like to think we matter more than rocks, but according to your commitments, we don't. To argue otherwise would be to make a value judgement, and you don't want to do that, do you?
Maybe you also wanted to include the subjective experience of feeling harm vs. a sense of well-being. But, according to your commitments, these are simply the result of stimuli acting on a body that is sentient (unless you are also concerned about the harm and well-being of rocks). Why should sentience give a body more value? It can't. At least, it can't latch on to some value that transcends its own subjective feeling.
I get it that you don't want to die, and so you feel confident in extending that sentiment categorically. But, show me your quantifiable evidence (since that is your standard of knowing) that says the desire to not die has any value other than mere sentiment. You can find 1,000 people who all say they don't want to die. But, that does not show that life is of more objective value than death, or that existence is somehow better than non-existence, according to your commitments. All it does it show that there exists 1,000 sentient collections of matter that prefer to stay intact. What value is that preference? What standard of "good" can you appeal to that doesn't reduce to some collection of matter?
Your sense of justice and fairness, what is it anchored to? Is it rooted in the evolutionary drive of the species? Why should this species survive? Have you looked around you lately at what this species is doing? Wouldn't it be just as easy to argue that a good bit of what this particular species brings to this celestial ball is so horrific that the advantage of its existence is at least questionable? You put yourself off as a rational person who sticks with the evidence, but I'm not sure you've sufficiently considered the evidence if you're arguing for the well-being of this particular species? We usually try to eradicate viruses.
Is there some inherent good in the human species to which you can point? You and I are simply collections of matter. What matters about us is nothing more than the matter by which we are constituted. The moment you make an appeal to what is fair and what is just and what is good, you belie the truth you say you believe. Either you are being inconsistent, or there is a standard that transends our constituent properties and sentient experience.
Now, you may not believe what I believe. But, unlike you, I am being consistent. Whether I am mistaken or not, I believe there is a God who is Love and created you and I. I believe we have value, not only by virtue of being created, but by virtue of being created in the image of the One who is Good. I get that you don't believe any of that. I get that you question the goodness of God, if such a God exists. I don't. So, when I say I appeal to that Goodness I am being consistent with what I believe.
You, on the other hand, have not followed through with the logical outcome of your own faith. I don't blame you. Absurdity lies at the end. Nonetheless, you still want to think in terms of what is right, or benefical, or good, or just. You believe there is nothing more than the physical properties of which you are aware, and yet, you still want to believe that something matters besides physical matter. Unless you're some kind of Platonist, who believes there is a transcendent good to which one can appeal, then your sentiment is an epiphenomena (or some such ad hoc tomfoolery you naturalists like to imagine) and matters no more than the grief of a rock.
Now, I'm not asking you to give your life to Jesus. But, at least give your commitments the serious reflection they deserve. And why you're reflecting, ask yourself why it matters if you reflect or not. What kind of collection of matter cares to reflect?