Feeling sad for you that things are going so badly. It is so hard when nothing we do seems to work, when nothing seems to get through. You are absolutely right. You shouldn't have to be the one trying so hard when he was the one who screwed things up. You'd think that he would be able to show a little remorse and a lot more effort in making things right with you. The total unfairness of it is completely enraging.
You won't leave, because of the kids, and that by itself is yet another example of the wonderful woman you are. I can only guess at what type of arrangement you have in mind. Please describe what you're thinking. Perhaps your plan is to basically change nothing, except that you will close off your heart to him and stop trying to make things better. Just living life for yourself and for your children without worrying or caring about your H.
Which is, as you well know, what a classic WAW does, for awhile, before she actually walks away. I'm not saying you would ever actually leave. Maybe you have the kind of strength that most people don't, and could live like that for many years. But your youngest is very young, and won't be 18 for a long long time. And you are attractive, and have strong sexual desires. Motive and opportunity.
So what am I trying to say? That at some point you would stray and that the whole thing would blow up and end in D anyway? Not necessarily, but come on, let's not kid ourselves into thinking that being a live-in WAW would be anything but simply a different kind of hell. I know that you might gain a measure of peace in not having to try anymore, and that you might gain a measure of revenge, but it's no kind of life for you.
I'm also wondering whether your H really realizes just how close you are to being gone. I'm thinking as a man here, and recalling my own situation vividly. I had no idea my W was so unhappy. Granted, she doesn't have your communications skills, and did not let me know in any way that I would understand how she felt before starting her A. I know that you have often tried to get your H to understand. The thing is, I know that my W THOUGHT that she had communicated her unhappiness to me. And in hindsight, I can see that she did, in some ways. But I had my own resentments, and did not treat her expressions of unhappiness as being more than, or even equal to, my own. And so I didn't respond, and didn't have my eyes opened until that terrible 26th of February when she said she didn't think she loved me anymore. I know you think you've told him until you're blue in the face, that you've tried over and over, and given him every opportunity to respond to you. But are you completely sure that the situation is crystal clear to him? Any chance at all that he has interpreted your attempts at communicating as nagging over little things rather than expressions of deep dissatisfaction?
I'm also wondering if there are any LRT-type options left. Any way to rock his world while staying with him. I am not sure what this might entail, am certainly not suggesting some A or open marriage. But is there yet a way to open his eyes to what he could be losing?