Sorry but those threads were old and I don't remember names. One guy's wife got pregnant by her affair and the guy was in prison now - he planned on raising the child as his.
I agree, DO NOT TELL ANYONE. If people suggest paternity tests to you, just say she is your daughter and that's all that matters.
You see, people CANNOT keep secrets. And it will hurt your daughter in the end, if she grows up with this big "secret" lurking beneath people's interactions with her. Kids sense that kind of stuff, but don't know where it's coming from. Better to keep quiet for the present.
As for her parents - if they already know she cheated, that's enough. No need to tell them the rest. And however nice they may be to you right now, know that in the end, usually blood is thicker than water. They are stuck with her, it makes them uncomfortable to be in the middle, and eventually (usually, not always) they drift off or even start believing the WASs lies about you. You just have to let go of it.
Don't ever joke about shooting OM again. They can actually use that kind of stuff against you in court to mess with your custody, don't give them any kind of opening.
And good for you standing your ground about him not coming to the house. Stick to that.
You know, I know your hope is for reconciliation, and don't take what I am about to say as meaning that I don't think that can happen - I think it could. But right now, today - what you need is a good lawyer. I would suggest you consult one asap. The paternity/custody issues, child support, your ownership share of her business, their ability to perhaps hide money from the business (you may eventually need a forensic accountant too) - you need legal advice asap. And I recommend you copy any and all available financial statements right now. Can you get any of the info on her business? You need to protect yourself in order to protect the interests of your children. This doesn't necessarily mean filing, or even letting her know you've seen the lawyer - but information is power and you need to find out where you will stand. And meanwhile don't do ANYTHING than can appear threatening - a well-deserved punch in the face to the OM could land you in jail, with a restraining order and supervised (limited) visitation - I've seen it happen here.