We are collecting all the videos and text abusive communications now. Have a ton of them now. We are looking for a way to strongly communicate to the client that we will not be tolerating this. We prepared an email but that that seems trivial compared to what he has done through his text and video communications.

Email is inappropriate because its easy to "hide" behind an email. Video call them and enumerate his abuse list while looking them in the eye. Quote their language word for word back to them and if this doesn't embarrass them straight away ask them to justify the language and then whatever they answer, tell them its not acceptable.

Put the spotlight directly on them and reveal the behaviour unambiguously - video call, not email.

You seem to have been really patient with them, probably to a fault. It would have been best to speak to them after the first instance of this and then drop the client altogether if they had continued.

Yes, our project manager was taking all the hits as this was a new project and hoping that the situation will change. Now he has shared us a few sample communications and we could not even hear the first few minutes of videos.