The truth about healing is that it requires people to develop and maintain boundaries. Note that I said "people". Both WS and BS actually have to learn what appropriate boundaries are and learn to live within them.
You had a really long post and I don't want to go through it line by line, so let's just take one example:
Last night was the icing on the cake. He’s still sleeping with me. And I’m stupid enough to let him. We got high together. (If you can’t beat them, join them.) He’s made it clear that it’s just sex. No feelings involved. And sure, why not let myself be used and hurt. Last night he gave me a complete mind fuck. Wanted me to beg him for sex. I played along.
So, if everything you said before that point is accurate, WHY is he still sleeping with you? Why are you getting high with him? And why did you decide to "play along" when you could obviously see that the "game" was demeaning? What did you think would be accomplished with that? that he would feel better afterward? Or did you maybe think he'd feel guilty afterward and start being nicer to you?
I'm not trying to be unkind here. I'm hoping you can begin to see how your own indecision and lack of appropriate boundaries add to the drama. For the past few weeks, you've gone back and forth on the subject of Hallmack. Today, you're calling him a "monster" but just last week warning posters not to say anything negative about him. You post that you're ready for a peaceful divorce so the two of you can start doing right by your children, but now here we are... with new drama just last night.
There comes a point where people need to DECIDE where they're going to plant their feet and then take ownership of that decision. To my view, you've BOTH been abusive in this relationship, neither has accomplished much toward healing, and reconciliation has clearly failed. In your "How" thread, you asked how to survive? But is that really the goal or do you both want to live???
In any event, my answer would be the same... ACCEPT that there has been too much damage in this relationship to overcome, wish each other well, and move on with your lives as cooperative but separate parents to your children. That puts a stop to indecision. Then, build some boundaries around your choice. Make it EASY for Hallmack to restart his life by giving him as much cooperation as possible in terms of settlement and divorce. INSERT BOUNDARIES regarding intimate contact and verbal communications. Do your business together by email and through parenting apps. BE PLEASANT. BE ACCOMMODATING to scheduling needs, but don't put yourself in any more situations which have the potential to degrade into any kind of emotionalism.
What happened to Hallmack wasn't his fault. If your account is accurate though, how he's handled it has been abusive. He's not here to defend himself, but I do remember him taking responsibility for the d/v incident, so we know at least that much for sure. You have also admitted to abusive behavior toward him. But two wrongs don't make a right. This isn't a game where you can be "even". It's real life and you two have real children involved. It's time to make a real decision, stick with it, and build some boundaries around it. It's no wonder that neither of you have accomplished any healing. Boundaries are the opening ante on that, not only regarding the other guy's behavior, but on what you demand from yourself.
Let him go. Don't just wish him peace, provide it to him by making his transition as easy as possible. YOU started this with your decision to cheat, and no matter how much you might wish you could take it back, you can't. Sometimes, cheating is just a deal-breaker and when that's the case, there's nothing left to fix. Hallmack will heal in time. So will you, and so will the children. Two peaceful homes are infinitely better than one dysfunctional home. You both did what you could with the tools you had on hand, but sometimes the timing is just wrong. I'm typically very pro-R when possible, so I don't say this lightly, but sometimes, it takes moving on to get to a place where you can finally obtain better relational tools. It won't save this marriage, but it will put you BOTH in a better position to be successful in the future.