In the past I have tried not to make hasty decisions when I feel like this. But I think the time has come for me to stand down and pull the (legal) trigger on my marriage.
There has been little disclosure on his part. It has been "I am unhappy and I don't know what I want" then nothing then TWO years later "I am seeing someone and I am going to tell the children". The bits of information I have gotten have been from other people (he was seen in town drunk with his friends chatting up women, he was seen on a date etc etc). Yes, he never said he made a mistake, wanted to reconcile, but he also never said the situation was done. He just came around, mowed the lawn, walked the dog, played with the kids and had a hissy fit every time I mentioned wanting to move on ... selling the house. Like he wanted to be single but he wanted the safety net of me here in case he changed his mind.
I think it is what he wants. He hasn't because he doesn't want to hurt me (unlikely) or he wants to avoid the conflict for as long as possible.
I have changed my thread title, but perhaps I am still making a stand, just a different one. A stand for me and not for us.