He made the decision to have the affair and have sex, and now he needs to deal with the consequences. Everything he says is "me me me". It is all about him covering his tracks.
He has shown you his true colours now, he doesn't want to lose his partner and child, and all he wants to do his protect his reputation.
You need to end the affair now, as this man is no use to anyone. It is too late for an abortion. You won't be able to put him on the birth certificate unless he goes with you to register the birth, but you should ask him for CM and if he refuses, then go to the CMS.
You can't make him be a part of his child's life, but if he is the decent loving father who can't bear not to see his existing child every day, then he should want to be part of your child's life. If he doesn't, then again, he is showing you who he really is.
I feel very sorry for his partner, but he made his decision to have an affair, as did you, and now you and him both need to face up to the consequences.
Good luck.