I currently live in a house with 3 other people, my girlfriend Julie, and 2 friends Bob and John. Outside of our household, we have a friend named Jane, who is our only friend that is married in our group currently. Bob and Jane are brother/sister respectively.
About a year ago, John and Jane started having an affair. It made everyone a little bit uncomfortable at first, but we sided with Jane because she was having some troubles in her marriage and told us that she plans to break it off. If we fast forward to now, she still hasn't broken off her marriage. Her husband was told a long time ago that Jane cheated on him, by Jane herself - but he does NOT know that it has been ongoing for so long. Her husband has made some mistakes in their relationship, which has hurt them before - but never anything like this. He does not deserve this treatment (As I believe no one does). Jane and her husband are also currently in the process of selling their home to buy their "dream home" for Jane, so she can have horses that she always wanted and lots of land. We are uncomfortable with this because we believe she does not deserve this as she has not been faithful.
Anyways, me, Julie, Bob, and our other mutual friend Sandra are planning on telling Jane's husband about it on Thursday, as we have been very uncomfortable, and we decided we weren't going to sit around and wait for something to happen anymore.
We have already told Jane's husband that we want to have a "Boy's Night out", to try to avoid Jane being there while we talk to him - but as of writing this, Jane messaged Bob, and asked him why we invited her husband out to a "Boy's Night", and it eventually came out the plan to tell him. Jane told him that it isn't our place to tell him and that she will never forgive him (Us when she finds out all of us are involved and decided together) - we are willing to risk that, as all of us refuse to sit back and let this happen anymore. As Jane knows the plan, we assume that John now also knows because we are sure they are talking to each other about it.
One thing that can happen now is Jane telling her husband before we have a chance. I kind of like that this happened actually because it gives her a reason to come clean and tell him herself which I think will end much better than if a group of people that are really just acquaintances tells him about it first.
But if she does not tell him first, we have to deal with John. As I said, John lives with me in my home along with Bob. There is no contract for him living with us, it's just a verbal agreement that he pays a 4th of the rent and utilities/bills. What I'm really worried about is retaliation as me, Bob, and Julie are directly involved and all live with John. Today when I get home I plan on taking pictures of all my expensive things, in case he tries to retaliate, break stuff, and then leave without saying anything. As he does live there full time and does have belongings in the house, I don't think it would be right for me to change the door lock code to prevent him from getting into the house to try to avoid this, so one question I have is how to avoid retaliation that will cost actual money to fix. I understand that there may be retaliation in the form of being ignored, hated, etc., but this does not concern me as I have already accepted it. Another thing is possible retaliation from Jane - if John knows the door code, so will Jane.
Another question that I have is, what is the best way for us to tell Jane's husband? We currently have a time set at 6:00 PM on Thursday to meet him for a "Boy's Night" at a local restaurant - our whole friend group minus Jane will be there to back each other up. This includes me, Julie, Bob, and Sandra.
I forgot to mention, Jane, and her husband also have a daughter who is around 2 years old. This is another reason we believe we have to do something, she is spending all of her time with John, cheating on her husband while her husband takes care of their child, and is about to buy a house (Serious financial debt) for her - we want to do something before he spends that money.
My distinct question is: How can we tell Jane's husband about Jane's affair?
My goals would be to keep everyone calm and peaceful, and avoid any expensive retaliations from negatively affected parties.
Answers that also contain a way to keep everyone on good terms would also be very greatly appreciated, we are all friends after all, but I know this may not be possible and is not a requirement to the situation.