Wow. That sounds brutal.
That said, you have to try to learn from this and understand that he's not the guy who is going to give you what you want, ever, especially not in terms of an honest conversation. Passive-aggressive, conflict avoidant people are impossible nuts to crack and are best left to their own devices.
I know how you feel. My ex is just like that. In the early days, I used to just shout at him, "I MATTER", because he did his best to make me feel like I didn't anymore. I wanted to still have my spot at the top of his priority list and he made it real clear that I got knocked down in his mind to the very bottom. He never told the truth or apologized for destroying our family. He just blocked out my rants and stepped over me to get to what he wanted.
After a few times of struggling to get him to talk to me or even admit the A or show an emotion or say something about the state of our marriage, I stopped. Silence became golden. It's been almost 4 years and I've never spoken another word to him about what he did since I finally got confirmation that he was with OW and I told him he was dead to me. I now only talk about the kids when I have to. I filed for D and never told him it was coming. Trust me when I tell you, with people like this, your silence is your power.
Chasing this dude around Costco, smashing his cart with yours, and demanding that he sit and listen - that will never work. That's like smashing your hand in the car door every day and expecting that one day it will no longer hurt. It's insane. It's what is causing you to trigger and have more of a panic attack than you should because his behavior is reminding you that he's no longer the guy you married. You keep looking for that guy and he's just not there.
Listen, I understand that seeing him causes a lot of pain and a lot of anxiety. I rarely see my ex, but when I do, I take off my glasses so he's nothing more than a blurry blob. If you don't have that luxury, you have to find ways to cope to calm yourself down, focus on something else, and pretend that he's not there.
This is all about you and your healing now. Property settlements and summer scheduling should go through the attorneys if the D is in progress. If you don't have a lawyer, think about trying to hire one to finish this off. You're not in the right state of mind to have to negotiate or deal with him on these issues. Every conversation will revert back to the "relationship" and to OW and that's just not good for you.
NC is your best friend. If you can't handle seeing him at Costco, walk out and go again later. I don't find any shame whatsoever in avoiding those things that cause pain. There are some things, like your kid's concert, that you can't avoid and that sucks out loud, but you have to be there for your kid. Shopping with that douche in the same store - entirely avoidable and something you should avoid until you are much more removed from this situation and the dust has had a lot of time to settle.
NC = no new hurts. Repeat that until it sticks.