I don't blame you for a minute about looking at your daughter to see if you can see the OM in her. I would think it was abnormal if you didn't. You don't think of her any less as your daughter, but with the current information you were given, that is absolutely normal and you are not crazy for doing it. And doing a DNA test on your daughter makes perfect sense too. I think you are handling this as well as one possibly could. I know you probably don't feel like it but those of us who have been on these forums for awhile read a lot and you have been handling this nothing short of amazing.
I would just echo what the previous posters have said regarding looking into your rights with an attorney regarding all aspects of divorce: custody, financial etc. Looking into an attorney does not mean you are divorcing your wife, what it does is arm you with information and helps keep emotions in check.
You do not need to worry about deciding on R or D anytime soon. As long as she is no longer involved in infidelity then you have time. You will change your mind between R and D probably hourly at the beginning and that is normal. I made a lot of mistakes early on because I didn't find this site until about 3 months past Dday. About the only thing my H and I instinctively did right was sending out NC letters, and transparency items and blocking their numbers. I offered R on dday if he was willing to put in the hard work. I had NO idea how the rollercoaster worked. I was in shock and couldn't imagine being divorced. I want you to know, that changed pretty quickly. His actions have been rock solid and he has been doing absolutely everything right, and yet once the shock wore off, there were days I wanted to D because I was so angry and hurt and he didn't deserve me. I also didn't go and talk to a lawyer. I didn't even think about that on Dday. Farthest thing from my mind. And I didn't go to counseling for the first few months because I was so overwhelmed and in shock I didn't want to talk to anyone. ANYONE......then the shock wore off and the counselor had to kick me out of his office every week or I would have never left. I could have stayed in there all day.
But that only was the case when I was emotionally ready to start talking about it.
So, I will probably get heckled for one of my thoughts, but that is ok. It's just something I have thought about in past when reading people's stories about finding out years after the fact.
One of the interesting things about your post is that you have 8 years of post A behavior to consider.
What I mean by that is a few things:
How has she behaved since OM died? Has she written you a timeline and has she been affair free for the past 8 years? The only silver lining that I see is that if she has been affair free for the past 8 years, that is a good start and you have 8 years of post A behavior at your disposal.
On my Dday, I had to start at day one hoping and praying that my H would be able to live the remainder of his life without being involved in anymore affairs. It was terrifying because I didn't know if he had it in him. I had to set my boundaries and then watch his actions and pray he would do the hard work to be a safe partner. In some ways, I would have liked to have had the A be a few years down the road where I could see that he was able to go 3 years without an affair so I could put a little more faith that he was capable of doing it.
My point being, if she has been faithful the past 8 years since the affair, I would put that on the positive column (there are so few things to put on the positive column on Dday so at least that would be one). The rest of us who found out on dday wouldn't be able to add that to our column.
Every WS deserves divorce. So whether it was 8 years of hiding the affair and letting you think your daughter was biologically yours, or in my case my H having sex with 4 OW plus other indiscretions, I have a hard time saying which one is more deserving of divorce. They are both really deserving of divorce. The choice of whether or not you will divorce is up to you. Is this a deal breaker or if she does the hard work for the rest of your marriage, is she worthy of redemption?
You will get all different answers of what you should do. Half will say R and half will say D. The choice is yours. You had zero say in her unilateral decision but you have a choice in what you decide.
Right now, it's way too soon to even worry about it. Just focus on the basics: eat, get your rest and get medication if needed, get exercise, and just take this whole S***fest one minute at a time and give yourself grace when you feel like you didn't handle something "the right way". Give that notion up immediately. This will bring out a bat shit crazy side of you that you had no idea existed. Please remember that is normal. Half of the time I don't recognize the girl staring back at me in the mirror. I had no idea I had such a sailors mouth. The old me would have horrified, but it is what it is. This rollercoaster is no joke. And you will be on it for years. YEARS. Just know that in advance. Whether you D or R, you will be on the rollercoaster until you have properly gone through all the stages of grief. So buckle up, hang on for dear life and keep posting.
Hope