Defamation - A famously high bar in the US. It has to be a knowing and intentional falsehood and have caused measurable harm if I understand correctly. That really seems like the absolute minimum of limitations to me if we're going to have a hope of maintaining a functional democracy. (We've got laws against false advertising as well ...)
Campaign financing - Notorious for enjoying minimal regulation in the US relative to other developed countries. Again I'm not sure how else a functional democracy is supposed to be maintained?
Invasion of privacy - I'm a bit fuzzy on this one. Are you referring to things like HIPAA, or to something else? Bear in mind that such regulations only apply to the professionals who are already authorized to view the data. To me it seems similar to the confidentiality you enjoy when talking to an attorney.
I already noted that I disagree with the existence of obscenity restrictions. The other ones you mention (national security, government employees, emotional distress) are fairly nuanced and quite limited as far as I understand. The vast majority of restrictions seem to boil down to the generic idea of knowingly and intentionally working to break some law that isn't itself related to speech.
I just can't seem to get too worked up over such a practical set of restrictions myself. Does it bother you that you can't legally incite a mob, or intentionally teach an aspiring terrorist to manufacture explosives? Or do you just object to my characterization of that as being a minimal set of restrictions? But if that isn't minimal, then what is?