Hi Ocean. I could feel the emotion pouring out of you as I read this. I am so sorry you are going through this, but I like the perspective you have on a lot of it! Shows that even through the emotions, you are clear thinking. Very important in situations like these.
As far as being embarrassed about vacillating between wanting to be angry at him and asking him for one more try, Don't be embarrassed, that is very normal. The thing is that when your brain is telling you that what you are going through is not okay, then you lean towards wanting to be angry. But then when your brain starts thinking that things could be better if he'd just recommit to the marriage, the lure of asking for one more try rises up. But the good thing is, that unlike so many LBSs, you do not act on those thoughts! Having them we all did, thinking that is not worthy of 2x4s. But if you were alternatively yelling and exploding at him, and then the next day going and asking for another chance at saving the marriage, that is when you would get feedback here to control your actions. You are already doing that! So rather than being embarrassed you should be congratulating yourself for a job well done.
I also get the whole, better when he is gone, not so good when he is there thing. When he is gone, you can settle down your emotions and move forward with your day. When he is there it is a struggle because the R between the two of you is not what you want to be, and that fact is front and center when he is around. So while I know you are scared about him moving out and all of the things that causes you to face (telling the kids, etc), I think when he does you will be better off for it. This man has made it clear that this is the best he can give, and as you have rightfully ascertained you deserve so much more than he is giving! Friendship. You can get that from anywhere. So I applaud you for not "settling" for his friendship in the hope it would turn into more later. Another indication that you are thinking more clearly than a lot of LBSs.
I also love you standing your ground on the L. Very important that this man doesn't gaslight you and manipulate you, and that is not going to happen with your L present! And yes, he is gaslighting you with the " fine, if you want this to be more expensive than we can do it that way. It's not what I think we should do, but if that's what YOU want." This is emotional abuse in my opinion. And it sounds like he has a long history of doing that kind of thing. So kudos for standing up for yourself and holding your ground on the L.
As far as the gym thing, Ocean I think you can trust your instincts on that one. This man sounds wayward. Wanting his cake (moving forward with D) and eat it too ("Hey, lets go to the gym as one big happy family!"). So do what YOU want. If you want to go to the gym as a family, with zero expectations involved, then do it. If you aren't feeling it, then don't. To me this looks like another manipulation by him. "Hey, I know you don't want to be friends, but if I can show you what a fun, upbeat friend I can be, maybe you will change your mind!"
Anyway, now is the time to double down on your GAL. Are you in IC? If not I highly suggest it. And just keep emotionally detaching from him. His gaslighting and manipulation will lessen as he sees that he cannot get you to emotionally react to what he says and does.
Keep moving forward!
M(53), W(54),D(19) M-23, T-25 Bomb Drop - Dec.23, 2017 Ring and Piecing since March 2018