Ranting and raving at him, finding hard to let go and calling the (bitch) OW once - and that's OTT and taking it very badly?!!!!!!! Not wanting her kids to play happy families with the bitch that wrecked her marriage? (I'm giving some emotions here, I actually save my worst disdain and blame for him.)

Don't think for a minute that it is better because nothing physical happened
It would have done, and he'd already crossed the cheating line with you.
Love, are you 19? You sound very young or naïve.
He cheated on her. This woman that loved him and had children with him. A life with him. Promises from him. Probably a vulnerable practical situation too, with kids involved. This man took away the family she thought she had. Left his kids. To fuck someone else.
She wasn't in the least bit OTT!!
And for those thinking he feels guilty...
Regret, maybe. He's got something no better now, the grass isn't greener plus he has the complication of splitting up his family.
But guilt? He managed to have an affair in the first place so I'm not sure his guilt-o-meter is all that sensitive.
No, I think this could just as easily be a case of a dog with two dicks.
Ex wanting to chat to him. OW letting him get away with lying to her...
My money says even if he wouldn't get back with her, he'd cheat on you with her.
It's not the present - it's the meeting her without telling you. 50 Shades of Wrong - disrespectful and suspicious.
I'd bail if I were you.