Regarding #2, reminds me of Wittgenstein's claim that, "If a lion could speak, we couldn't understand him", because for Wittgenstein meaning is use, and lions would have different use for words than we do since there is no shared culture or biology. It would likely be even more incommensurable for sea creatures who don't share dry land with us.
I have some problems with Wittgenstein's philosophy when applied to human rationality (I think cross-game invariant structures do exist) but here I think it's an apt observation and you could very well be right. Nice!
You might be right. I dont think its certain though. Humans seem to be able to communicate across language gaps in ways we can't with animals. Things really could be that different. For example, all human languages that we know about have some idea of a who doing something to a whom, even if they express it in drastically different syntax. For all we know (I'm just making this up, don't take it too seriously), whales might experience the world as a stream of objects. Maybe that's perfectly fine for whale existence. But we can't even really conceptualize that! And how would we know, anyway?
Eh, if I were a mad scientists with a unaligned AI and a wetlab I'd keep jamming more and more language related genes in animals to see if anything interesting happens. I know there's been some work around the NOVA1 gene that is showing interesting results.