Yep I agree with the grey rock technique it worked for me. He’s knows his actions provoke an emotional response from you which is exactly why he does it.
My ex was exactly the same, as soon as I’d get a text or the phone rang my anxiety levels went through the roof, I’d reply straight away eying to either defend myself against whatever ludicrous thing is been accused of or trying to make mr ex understand their actions were affecting our kids but it was pointless.
Eventually I just ignored it all, didn’t reply to anything other than the kids welfare, pick ups/drop offs. Any manipulation with regards to the divorce settlement/maintenance etc Went through my solicitor.
I blocked all forms of communication other that text or email, WhatsApp allowed them to see when I was online, read messages etc. My ex even switched to using used other apps such as Snapchat to actually locate my location! if they rang I let it go to voicemail that way I could determine if it was important or not.
The technique I adopted was to read the text/email and allow myself hours or even days to determine if it deserved a response. Often I didn’t and even when I replied it short and business like or just an ‘ok’. If it was an accusation I would ignore, which often led to outbursts and rage, I’d simply turn off my phone, go for a walk etc..
It takes time and practice but they get bored eventually and realise you won’t be provoked into an emotional response.
Good luck.