That's one way of putting it I guess. Personally, I would avoid using the term "social contract" in this case and refer to the the fact that morality only is possible to the single, thinking, autonomous individual.
To the extent that any other individual ("animal" or else) is able to reason, their individual moral rights should be fully respected.
(it get's trickier to explain the actual details once we get to things such as emotion and human handicaps, but this would apply even then)
Well said. And yes, it's tricky mainly because of our ignorance. We don't know what we don't know regarding consciousness, the brain, and how that impacts our understanding of morality. We can't even agree on which moral framework is the "best" one.
I think we can and that it's important to emphasize that we can, but I agree that it is very difficult to find any such agreement and that it would take a ton of work.
I try to make the same arguments. Hopefully we can at least make progress toward that goal. :)