Hiya!
Does your friend know about the Mumsnet threads? I hope she knows what an absolute star she must be to be supporting you and giving you a safe space like this.
As others have said you're in a bit of an adrenaline crash now. The fight or flight you've been under for so long has suddenly lifted and that can be very disorientating. Takes a while to adjust and rebuild your confidence and independence that he's been systematically breaking down.
Allow yourself that time.
Reach out to family and other friends.
And to colleagues/manager/HR. They should have policies in place to support you, because you need support and there is no shame in vulnerability.
And beware the inevitable attempts to reel you back in. He's tried using the mutual friend, who'll have none of it. He'll try anyone else you have in common, so ensure they know exactly what he's done and your decision, so they'll be prepared.
Be vigilant about your security. You shouldn't have to, but sadly this may not be end of it.
And stay resolutely blocked on all channels.
He may use any tactic he can think of. They're just that, tactics.