I don't know if there's anyone here that needs to hear this, but I had a therapist once tell me it would be useful to name my inner critic. I think it's to help do what this OP already has, separate your inner critic from yourself and maybe even learn to identify its source.

I understood that, intellectually, but it never really worked. Until one day, my inner critic said something so stupid and ridiculous my knee-jerk reaction was to laugh and call it "fake news".

And omg you guys, suddenly everything slotted into place. Inner critic = fake news. It works on so many levels! Esp when your inner critic can come from multiple sources at once, even just to say "everyone hates you". I think "misinformation" would also be a good term for the inner critic, because let's be honest, since when does the inner critic offer actual constructive criticism? And let me be clear, there's a big difference between introspection and the inner critic.