DG,
Cheating is a choice not a consequence,
No matter how bad your marriage was, I believe were not your case, no matter how recent big changes affected your life; there is always other way to deal.
No matter how she was feeling, you were always emotionally available for her to the point to make you feel so jealousy that you rather to fix it in therapy before doubting about her doings, for God sake your even told her how you was feeling and she kept lying and planning!
All her cheating is not your fault!
The way you are reacting is perfectly normal. There is nothing wrong with you!
Well, this is hopefully about to end next Wednesday. IMO this is how it is going to be like:
MC will try by all means to make an excuse for your wife not giving you the PS, be prepared for low punches (why are you doing this to your family, daughter), emotional threatening (you will never get someone to love you the way WW does, your Daughters will recent you forever) and blackmailing (Your wife will find someone that really care about her, etc).
Next will be the moment when MC strongly recommends to your WW to not give you the PS and to you to not look into the phone and computer, by saying, you are not ready, nothing good will come from this, what you see can never be unseen, etc.
Expect some resistance from your wife to give you what you need.
Make crystal clear to her and MC that you have done your part of the deal and are expecting to your wife do the same. Remind her that you will assume the worse and never talk to her again if she breaks the deal. Let MC and WW know that keeping you from the truth have put you in so much more pain not letting you heal, From MC trying to blame you for WW doings and making this ordeal about you was very unprofessional and has done more damage and burned more bridges than doing nothing. This was supposed to make you feel save for what happened, accept it and try to put the shattered relation together, not pointing fingers and making a fools contest about who is fault for something you don’t even fully know.
IMO if possible, take control over the situation being very calm about the whole session and then, if you are ready, you may ask in front MC, to have a neutral environment, some questions to your wife about thing you cannot get from the devices, like:
Do your ever said that you love him? She, of course, will say that she did but didn’t mean it, well she felt that way even that now she thinks/knows feel different.
If you have phone records you may be able to know when it started for sure, and you may ask were your phone calls with him worse than text/emails?
From IT guy you will be able to find out if they Skyped/Face timed but your will never know what was about? If cybersex took place, etc.
Any other thing you need to know this will be your last chance.
One last chance, very unlikely but that must be contemplated, is that WW comes clean at next MC. Expect minimizing, TT and Blame shifting. This will be the harder scenario. No matter what keep calm and get the PS to check it latter. If this happens, it will show a big improvement from your wife.
Last consideration: No matter what happen at MC ask your wife to come clean to everyone she involved in this mess.
Realize that this is not fair, life is not fair why would your situation will be? Your relation with your wife will always be unbalanced, no matter what, so when you finally Divorce her being apart will heal you.
Notice that she was/is/will be part of your life as is the mother of your children, so be gentle and fair when D, ask her to civil and ask her for her fully cooperation to make it easy and faster as possible. IMO she will try to get back to you for a long time even after D.
Last thing, when you have the text and emails, don’t forget to handle a selected ones sent by OM to his wife, just in case he lied her way out the woods by blaming your WW, minimizing, saying it all was fantasy and not that bad, never sexting, etc.