1) Do some reading on 'co-dependence'. It might be relevant to your sitch. I believe the book Codependent No More is a good place to start.
2) Delve deeply into the Healing Library (link's in yellow box, upper left of SI pages). Start with the BS FAQs. Be sure to read about the 180 and see if it fits for you.
3) Consider IC for yourself. Right now it seems like you're trying to spend your energy in understanding what's going on an wondering about the future. A much better bet would be to separate yourself emotionally from your W and face the grief, rage, and fear you feel directly.
You heal yourself. Your W heals herself. Together you heal your M, if that's what both of you decide to do.
The feelings are really hard to deal with - IC can help.
4) Have you outed the A to om's W? to the Church? Bringing the A out into the open also brings it out of the fantasy world the A lives in. Tell om's W that om is cheating.
5) Demand that your W get tested for STDs now and in 6 and 12 months. If she's uninfected, I would skip getting myself tested, but a lot of people I respect here say you need to get tested yourself, whether she tests OK or not.
6) One thing you should get from the Healing Library is that you can't love a WS back into the M. You MUST set and enforce boundaries.
To R, the WS must be committed to doing the work necessary to R. That includes, in virtually ALL cases, 1) establishing NC with the ap; 2) answering questions honestly and fully whne they are asked; 3) keeping the BS informed or whereabouts, activities, and companions at virtually all times; 4) IC to change the thoughts and feelings that allowed the WS to cheat; 5) MC if both partners deem it appropriate; 6) special requirements that differ for each individual (for example, my W has to initiate sex sometimes, and she has to arrange dates at least 2-3 times a month.)
Your W sounds unremorseful, since she's apparently still in contact with om, since she doesn't answer our questions, and since she still keeps FB, email, etc. out of bounds for you. She's not a candidate for R right now, no matter what she says.
That's why the 180 is probably for you. The 180 helps you find your strengths again, helps you see you're a loving, lovable, capable man who can live without her, and helps you set boundaries.
Those boundaries are your requirements for R. You can observe if she meets them or not and respond as appropriate.
There's no way to guarantee a perfect life, but the longer she meets the requirements, the more likely it is that she'll continue to meet them, and your trust level will increase - but give it years.
My W started doing the work of R on D-day, and she never wavered. Even so, after 31 months, our MC says my continued mistrust makes perfect sense.
But if her A predates your relationship, and if she cheated with a married man while she was single, your W sounds like a mess. He recovery will probably take an especially long time and be very difficult for both of you. Do you really want to stay with her?