I’m sorry you are going through this.
I have had periods of my life when I suffered from anxiety and PTSD at Mass, and I didn’t even have an abusive ex or other abuse history in my past. I just felt very different from everyone at the Mass and I was struggling with anxiety on a daily basis in many areas of my life, and was not attending in the parish I had grown up in, or any place close to it, and the parishes I was in seemed strange in many ways. I was not happy about having this problem and it did eventually drive me away from Mass for a long time as I got out of the habit of going.
It’s good that you still want to go to Mass or at least Adoration, and aren’t letting this problem take you away from Jesus.
I think going to the Adoration chapel is a good start. I also think that you should try to attend as much Mass as you can sit through before having to leave. Even if you can just get through five minutes, it’s a start. Once you can do five minutes, try staying for 10 minutes. Or if you have to sit out in the vestibule and just go in at Communion time, that’s fine. (Talk to your priest about whether you need absolution before receiving Communion, if your anxiety has caused you to miss a lot of past Masses on Sunday.) Maybe mention to your priest that you are having this issue and see if he has a suggestion, like a separate room you can sit in and hear the Mass, so if you get emotional you can just cry or whatever without feeling like you are on display.
If you have a supportive friend who can accompany you to Mass, that might also help. You can start associating the Mass with your friend and not so much with your ex.
I am happy that my issue has gone away now and I no longer have anxiety problems at Mass. I wish you the best in resolving yours. I will pray for you. God bless.