And I know in my bones that if he were to give us some time, we would get to a better place than we have ever been.
You don't know this. It isn't possible to know this. It's sad, and it is painful, but no matter what good times you have had in the past, it might very well be better for your H and you to be apart. It might, through no particular fault of yours, be a healthier and happier outcome for your H to be single. It may not - who knows - but that is something for your H to discover for himself, and you to discover in a parallel process - not for you to decide in advance for the both of you.
I think if you go into these interactions with 'no matter what you are saying to me about what you need or want, I know better, and I know the best place for you is with me,' then it is going to come off as suffocating, controlling and patronising. I know you don't mean it that way, but I think that is the effect it going to have.
I think you have to give him his freedom. If he wants to leave, let him. If he wants to D, let him. If he believes his best happiness is elsewhere, let him find it. Concentrate on finding your own best happiness with what is available to you right now.
This is unimaginably difficult and painful. I am so sorry it is happening to you.
