I agree with every fact you said yet my conclusion is that humans are valuable. Why? Because your frame of reference is the world, mine is the known universe. Humans are so fucking unlikely. Matter that somehow can experience its own (and others) being is so crazy unlikely I feel anything other than valuing it is just wrong.

In German we have a word called "Zweckoptimismus" that would translate to purposeful optimism. It is the optimism of someone who knows the world isn't good, but accepting it as bad would make it even worse, so you operate under a defiant optimism without ignoring the reality of the world.