I think 3) is your strongest point, may I try to expand on it?

I wonder, what is Sam's response to utility monsters, small chances of large effects and torture vs. dust specks? In saying that science can answer moral questions by examining the well-being of humans, isn't he making the unspoken assumption that there is a way to combine the diverse "well-being-values" of different humans into one single number by which to order outcomes, and, more importantly, that science can find this method? Then the question remains, how shall science do this? Is this function to be found anywhere in nature? Perhaps in the brains of conscious beings? What if these beings hold different views on what is "fair"?

I simply can't imagine what one would measure to determine what is the "correct" distribution of happiness, although that failure to imagine may be on my part.