Do you know, I'd maintain a stony silence for now.
Yes, it could be that he's not quite grasped the implications of the whole thing. I don't think so, I have to say. I think the 'when I come back' attitude is a lot more than that - I think this man, unsurprisingly, is the same entitled, selfish, arrogant knob who thought he could have an affair and you'd take it lying down. Now he's moved on to thinking that yes, you're having your little spit the dummy moment - but ultimately, he's smugly secure of the 'fact' that you need him, want him, can't live without him etc. etc. And he'll be back. He may even be enjoying the drama, because at the moment that's all this is to him. Not his future at risk - just a bit of (yes, almost exhilarating) drama. He's probably already thinking smugly of the moment when you call and ask him to come back.
Why else would he think he could get away with an affair, with shitting all over you? Why would his essential personality have changed so drastically in a short space of time?
I'd have a long think about what his reaction probably means. It isn't great.
What is really important here? You, that's what. What YOU want. Don't fritter energies and anger on him. Most importantly, don't contact him to 'make your point' again - all he will see is you getting in touch, you being riled and upset, you responding. He thinks he'll be back? Well, more fool him. Because you aren't going to spend your time ranting down the phone at him - you're on more important business, the complex, delicate mental task of trying to work out, really and truly, whether you want him back.
If he knew that, if he could see inside your mind, if he wasn't such an arrogant prick that the thought you might be serious hasn't entered his head, he would be crapping himself.
Forget his movements and actions for now. If anything, stony silence is the only thing that probably will rattle him, to be honest.
Instead, get thinking. Two key areas:
Him. Could you return to loving this person wholeheartedly after this? Is he worth your love? If you took that path, do you think you'd regret it - look back in 20 years and think - he wasn't worth it?
You. Work out all the practicalities. It's a sad fact that people stay in the wrong relationship because they feel trapped, financially and physically, and it's easier. But it's rarely actually that strong a trap. Work out FIRST how you would not only survive, but THRIVE without him. It'll be easier than you think, if exhausting for a while. Then, when you aren't paralysed by fear of the unknown, consider point 1 again. And weigh it all up.
I hope you make the right decision for you, but a not-so-tiny part of me hopes that you make the decision to kick him into touch - because I would give anything to see the look on his smug little cheat's face when you politely and regretfully say, I'm sorry - you won't be coming back.