Keep all documentation and wait. It is now up to him to prove you did the wrong thing. It's now his word against yours so he has to come up with the proof. It still sound suss and if it goes further I would be getting someone independant to make an assessment of the problem. Pulled out cords will not make you loose data.
If he has not got legal advice by now you wonder why not. He is trying to bully you into paying and hoping you will cave. It's a good thing you got legal advice so early.

Let him stress about it instead of yourselves.