Choco, you have the moral high ground. Your ground is so much further up than his, that you wil be needing gas and air sooner than you think. And as for him, well he's so very far beneath you that he is literally dancing with the devil.
Everyone around you knows this.
It is simply impossible for anyone to exaggerate the situation.
He is married to you and has a child with you, got pregnant with you and then left you for another woman before your second child's arrival.
They are the plain facts.
They can't under any circumstances be exaggerated. They can't be excused.
Anyone with a pulse know this. It so confirms that you are so very well rid of him. The more he tries to paint you as the unreasonable one, the more pathetic he will come across to everyone you both know.
Is there any of that cheesecake left? Take a big piece and enjoy, you have your boy home and hopefully no need to think about your ex for a few days...
Wish you could name and shame him. I don't live in the UK but I'd happily fly over to kick his proverbial arse!