Most of your expositions are pretty good, but this one is lousy. You've captured the logical form pretty well, but the commentary does not make a very good showing of critical thinking.

(1) Between do-not-resuscitate directives and decisions to allow brain-dead patients to die, there is ample evidence that lots of people behave completely consistently with the idea that brain-dead patients do not have basic moral rights like conscious people do. Your commentary phrases it as a conditional without arguing for the antecedent, but if you don't actually think the antecedent is likely, why do you waste our time with all the elaboration? So the implication is that the antecedent is likely to be true when evidence is that for very many people it probably isn't.

(2) You introduce hypotheticals with all kinds of different complexities than you get with embryos. For instance, you talk about "someone" killing the patient with a cognitive disability. Well, why is the patient being kept alive? How certain are we of their condition? Who is this someone doing the killing? Does this someone have an analagous relationship to the patient that a person killing an embryo might have with the embryo? This muddies the issue so terribly that it isn't particularly instructive as written.

(3) You bring up a complexity of "if fetuses possess [consciousness and sentience]", except it's irrelevant to the argument under discussion because that has not any fetus but "embryos and beginning fetuses" at which point the structures of the brain that are required for anything remotely like sentience aren't yet in place. We need more research to define what cognitive states correspond to which developmental milestones, perhaps, but it's already abundantly clear that at 8 weeks the architecture is not in place for sentience. (For instance, thalamocortical relays are completely absent.)

An equally good parallel (i.e. not a very good parallel) would be to ask if recently deceased people's bodies have fundamental human rights--after all, they do still have plenty of living cells, including some neurons, even if the person is dead.