Well I'm new here but I've read a bit of your situation so I'll give my opinion. She is clearly still in an affair, you have access to her phone records and they show communication with OM. She is still seeing you as plan B, she does just enough with you to keep you on the hook. She is in no way turning around, she even suggested you volunteer and work alongside OM. This should have been an immediate no response from you, instead you said you would give it thought. This shows weakness on the ultimate level in my opinion. Also, why are you guys still in the same household? I understand she homeschools the kids but still, your enabling her wayward lifestyle.
Like i said, i am by no means an expert but you need to step back and look at things differently. Stop doing activities together, i.e. Concerts and things with the kids. She needs to see what life will be without you. You are giving her the best of both worlds. I know its hard because of the kids, especially S8. You need to contiue to shoe him love and he will adapt. You cannot cover up for wife and make it seem like she is perfect. This is just a quick reply from what I've seen, ill read further into your past and see what else i come up with.
M:26 WAW:26 T:11 M:7 D:3 BD 1 10/16 I love you but not in love BD 2 2/18 I love you but... W moves out 3/18