Hope your day goes well?
He's following the Script. Probably prompted by his mother understandably anxious about losing contact with grandchildren plus realising now he's been found out just how much he is going to lose.
Be prepared for nicey nicey to start with. The smarmy wheedling stage. The flowers and texts are already happening. Regrets, apologies, tears, 'can we try again, I'll change, promises, think of the children, the family, let's have another baby' bla bla bla.
Then as that doesn't work and he realises he has truly lost control over you (which is how he saw your relationship), the coercive emotional blackmail it's all your fault stage. 'How could you destroy our family, keep me from my children, you're nothing without me, who'd want you now' bla bla bla.
Then as that doesn't work, the threats stage - 'I'll harm myself if you don't ...'
Be hypervigilant that doesn't descend into 'Harm the children. Harm you.'
And the sabotage stage you may not even hear about. Contacting your family and friends behind your back. Selective sharing of communications between you. 'Look what I had to put up with. What choice did I have. She's crazy.' (My ex SIL's next boyfriend did that to all of us).
So do be very businesslike about all your communications with him, preferably email rather than text or phone/Facetime etc. Keep them all. It's going to be a challenge, but control your language and the tone of the comms, because having them to hand should support you and your decisions if you ever need them as evidence.
All the very best - there's an army at your side.