I think Edwards believed that he was the father all the way up until he did a DNA test, which was probably performed shortly AFTER they got caught by the Enquirer at the hotel last month. I have no doubt that Hunter told him he was the father, whether or not she actually believed it. I also think that he was continuing to have sex with her off and on until they got caught by the Enquirer at the hotel ("come on honey, just one more time to remember you by").
Edwards probably told his wife about the affair after the Enquirer outed them last fall (even though the MSM refused to mention it, there is no way the Mrs. didn't hear about it), but assured her that it was over. He probably also told her that the baby could not be his because the affair was over long before she got pregnant. That was part of the reason he was in such a panic when the Enquirer caught him at the hotel last month (while the Mrs. was out of town raising money for cancer research).
I also believe that he had plenty of opportunity to get a DNA sample from the baby when Hunter was not looking (probably the night that he got nailed at the hotel by the Enquirer) and that it would have been incredibly stupid of him not to do so given the facts.
The fact that he has now denied paternity and at the same time professed his willingness to take a DNA test almost certainly means that he has already done one and that it came out negative. (He probably got the results shortly before his confession interview, since he need the results to determine what sort of confession he had to make.) If that is the case, then he has probably also told Hunter that he knows he is not the father and that she had better go along with whatever he says if she ever wants to see another dime.
I also believe that Hunter had plenty of opportunity to get a DNA sample from Edwards when he was not looking and that it would have been incredibly stupid of her not to do so given the facts. She needed to know how much leverage she really had. If her DNA test had come out positive, she would have told Edwards. If her DNA test came out negative, she never would have told him about it.
I just don't think there is any chance Edwards would profess willingness to take a DNA test if he was not already positive that the baby is not his. No matter what deal he has with Hunter, no matter what promises he has made and no matter how much she may be in love with him now, eventually she is going to demand more than he is willing to give. When that happens, if there is any chance he is the father, he will be named in a paternity suit and be forced to submit to a DNA test whether he wants to or not. He knows that. He may do most of his thinking with his little head, but he did make a fairly successful living as a trial lawyer.
You are probably right.