Is there a reason why you would not want to go through mediation to resolve custody issue, instead of filing?
I have heard very similar sentiment regarding indifference being worse then anger. Your wife certainly has a lot of anger.
Regarding initiating conversations and texts as a 180, i am not so sure. She is involved in affair and she has ended things. Right now I think you need to give her space. Text should always regard kids. (How are you and the kids doing would be appropriate). I can see your wife getting irritated with polite formal texts at this point. It sounds like in the past, she was looking for conversations to help connect you guys. Subjects on a deeper level involving the two of you. At this point, it is too late unless she initiates. You know eventually her affair with OM will burn out. Right now I would keep your temper under check. Remain polite. Let her pursue. Avoid all relationship talk because you guys are way to volatile right now.