OP I am so so glad he has finally moved out, and you had a nice first evening of peace.
Texts from him like the one last night - he is NOT your friend. Only reply to texts about the kids. Factual text replies eg about contact, illnesses, etc. Nothing more. Any other chatter from him just ignore, even if he's trying to rile you into defending yourself, just grey rock/ignore.
Despite my ex apparently being oh so miserable living with me he still seemed to think I'd entertain chit chat via text with him. No fucking way. He is no longer any of my concern other than in terms of trying to get him to coparent (mine does ONE night a week now we are several years post split btw, and it's never on a weekend night).
Get a parenting app downloaded, offer whatever you think would be best for the kids and keep all messages focused on what is best for their well being eg a set routine. He will quickly do less and less. Don't overly react.
Also - if you ever have plans when the kids are with him, don't tell him or the kids. Or he WILL cancel. Guess how I know. 🙄 Finding a good babysitter will be of way more use to you OP than he will be.