However,
1. You are assuming a lot in the sense that you assume presence of intention -- not something guaranteed to be a feature of an alien civilization, which is, well, alien. People think that anthropocenrism only applies to body shape and having legs, because the way it tends to express itself in popular culture is robots on legs and human body shape in aliens.
And same point goes to communication; just assuming you could is a big leap.
2.Bold assumption that they are self limiting. I think the real question is what , exactly, tends to limit it. I think the answer tends to be resources, which is the foundation of dark forest argument theory to begin with.
What I am saying is that it is not a rebuttal you think it is.
3. :D yes
4. You may be again imposing human perspective on as scale that goes a little bit beyond it.
I will end with a.. semi-optimistic note. I am not sure dark forest theory is valid. We are speculating mostly based on human tendencies. By the same token, I posit that we are about as likely to be turned into an art exhibit by a passing alien artist not unlike some ants that had molten metal poured into their nests [1].
Any real alien reasons would be alien to us.
[1]https://laughingsquid.com/ant-colony-sculptures-made-by-pour...