There is so much going on in your OP and responses. Understandably, because of what that arse has put you through, you are muddling the issues.
First is your shock and feelings of betrayal at being lied to and gaslit. I'm so sorry that happened to you. It could absolutely happen to anyone, even the smug, unsympathetic posters on this thread. I hope that you are healing slowly and being kind to yourself, but that sense of injustice is perfectly natural.
Second is what you feel is reputational damage, with him continuing to lie to his wife and possibly others. Telling people that you knew all along, or that the affair was your fault, or whatever else. Well, he will do all of this. He's a lying, scheming prick. This may or may not have any realworld impact for you, at least for the next few years. It depends how much you run in each other's circles. Some rando you don't know thinks you are Jezebel - I mean, that sucks, but does it matter? Maybe it does, and if so you should seek good advice before taking action or posting anything or contacting him.
Next is the baby - and congratulations on your little one. You either need the money or you do not. If you can live without it, then that is the easiest answer for now. You may get away without interference in your life and the child's for a time (depends on the laws where you live). And you can change your mind and claim CMS at any time - at least in the UK.
You dc will have a right to know their Dad. In seven years, or twelve, you may be dealing with a child who wants to know Dad and have a relationship with him. And you will need to deal with all those old feelings of unfairness, because this man will lie to your child, will blame you, etc. Your child's realtionship with him, if any, will be their own.
All steps you take now you will need to one day justify to your dc. So beware of your motivations when you take decisions - your anger is fully justified, but maybe not always helpful to you.
I think contacting his wife was a perfectly fine thing to do - she should know what he did - but it wasn't one that will help you. No worries about that, but from now on take decisions only in the best interests of yourself and your dc.
So keep the receipts, all the communication with him in written form. Someday your much older child may need or want to see that.