i don't think i agree with you, think. (you're going to outmanoeuvre me in every way if i go in too deep here so i'm going to duck out if it becomes unmanageable for me) but:

a) your understanding of what he calls "human flourishing" is pretty shallow -- i think he's talking about something he isn't defining, because it isn't really the point of the proposition. "physical wellbeing" is a rather meaningless term for someone like me, considering that everything IS physical anyway, so if i said it, it'd include mental as well as "physical" wellbeing. but i think it is in a VERY ROUGH BUT SUFFICIENT FOR NOW way equivocable to "happiness".

b) there are many ways to promote human flourishing. yes. that doesn't make his point meaningless. we should be able sensibly to determine what things promote human flourishing and what inhibit it. just like physical health. i'm pretty much repeating exactly what he said. why does this mean all that he's saying is insubstantial?

c) what exactly are you saying in the final sentence of your first post? if we don't know something's wrong, we can't fix it. are you going off some other video/quotation that i haven't seen/heard/read? what he is a problem with is not visual signs of internal suffering, but any internal suffering -- he is claiming, maybe over-optimistically, that we should be able to tell (better than we currently are telling) when someone is suffering, and with some actual investigation and intelligence, sort out what causes it. what you're saying about this pill is insane and absolutely not what he would say, unless i'm very much mistaken.

d) he kind of goes of this superficially (do remember that he has ~15 minutes to make this speech), but he is saying that morality concerns the experiences and wellbeing of creatures able to have experiences and wellbeing. that's a little bit of a leap, but, i think, a reasonable one.