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.
there's this notion that things are so arbitrary and beings are so different that one can't understand eachother. I find this fascinatingly wrong.
No, we can't understand lions because lions are kinda stupid. We can't understand lions also because we haven't researched them enough.
My bet: once "beings" cross an IQ threshold, they can start to understand each other.
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!