I hope you know that the strength of emotions being expressed by people in your thread is not criticism of you, but anger/outrage about what has been done to you.
You have alluded several times to your fear that your wife might simply walk away without a care, and as a result of that, you feel like she holds the power in this situation.
I want to offer a different perspective on that. Your wife has already told you that she does not want her AP's wife knowing about her affair with the AP, because she does not want people 'talking'. Think about this for a moment: if your wife is scared of her AP's wife finding out about her affair, how much more afraid would she be of her affair becoming the talk of your small town? That every time she walks into Walmart, people point at her and snigger? Image matters to her, and she has a lot to lose if she becomes known as a 'scarlet woman'.
Further, can she really walk away from a twenty year marriage and family without erasing twenty years of her life, and going back to square one? What would she have if she walked away? A reputation as a cheat, a lost marriage, a lost family, and a lost future. Do not underestimate the value of that to her. Whatever crap she believes about her affair and 'what she had' with her AP, she also knows that if she was to walk away and attempt a new life with the AP, it might last two months and then crash and burn. Walking away is a Hell of a gamble for her, and it is one that she is not willing to take, because whatever garbage she spouts about the affair, she wants the security of the marriage and family, and she is keen for word of the affair to not hit the streets. Particularly not in a small town.
So do not run away with the idea that she can walk away whenever she likes, and potentially start a relationship with her AP. She knows damn well how the town would judge her, she knows how it would impact you and the kids, and she does not want to write of twenty years of her life to take up with with an AP who was dumped and divorced by his wife. She knows that if she leaves you, her life could turn to crap in a matter of weeks.
I believe that what she wants to engineer for herself is a return to the security of the marriage and family, with nobody else knowing about her affair, so she can pretend to other people that it never happened, and have her affair accepted as a temporary episode of no consequence in the history of the marriage. She even told you that lots of people have affairs, as if hers has no consequence.
So here is the thing; as much as you may feel like you have no power because she could 'walk', the truth is actually the opposite. If you throw her out and tell everyone in town what she has done, her world will implode. And the chances are that she knows that she and her AP may have worked in the non-committal environment of an affair, but she also knows that they would not work as a couple. So if you threw her out, what would she do? She herself said she would be single. Yes, that could be bullshit, but it may be the truth, if she knows she and the AP have no future as a legitimate couple.
Your wife's immediate options are you and a family she has put twenty years of her life into, or an apartment on her own, and a catastrophic loss of reputation. Her future is entirely dependent on you, because you could blow her image and life totally off the rails by kicking her out and publicising what she did. Is it any wonder that she keeps trying to give you the impression that she holds the power? If you threw her out on her ass, she would be in trouble, and she knows that.
You have more power than you think, and she has much, much less than you think.
Edited to add:
You have said that you have grilled your wife about the affair every day since you found out about it. If she really wanted a future with her AP, and she thought they really had a potential future as a couple, why would she put up with constant interrogation rather than heading into the sunset with her dream man? Think about it. She has stayed, and and she has put up with the questioning, because she knows that her best option is to stay married and to maintain the family. If the AP was really such a wonderful guy, and she thought she could run off with him, she would have done it. The fact that she has stayed proves that she knows their affair was nothing solid or real.
When she talks of 'what they had', it is like talking about the shape of a puff of smoke. A temporary thing that will not last. Affairs can appear to be fantastic things, because the relationship exists in an unrealistic bubble where bills do not have to be paid, house insurance is never mentioned, pensions and 401Ks are not considered, and responsibility is abandoned. Affairs are the equivalent of two children pretending to be adults. And your wife knows that. She knows that her affair was an insubstantial and temporary trip into a video game. Not real life.
Your power in this dynamic is your control over whether or not you let her back into the marriage and family, or you bar her return and make her start all over again in life at the age of forty, as a known cheat in a small town. She knows that. How much power does that give her? How much value does a forty year-old cheat who destroyed her marriage and family have on the dating market? And how many men worth dating would consider dating a woman with a track record like that? Your wife knows the answers to those questions, which is why she is not going anywhere.
[This message edited by M1965 at 1:42 AM, Saturday, August 28th]