So how does this affect causality, if at all?
I'm not sure about causality, but it would seem to have ramifications for simultaneity, which since Einstein has been thought to be meaningful only within a particular frame of reference. Referring to simultaneous events across interstellar distances is supposed to be meaningless.
I don't understand the details, but that's what the theory is supposed to imply. Not sure where quantum entanglement fits in.
It doesn't, at least not in the sense that most people think of it.