Assuming you and their relationship with you was important to them, I'd say a "normal" poly person (if the people on this forum are representative) would take a step back in order to deal with the situation without hurting their partner further. While they may not be able to address all the hurt/fear/anxiety at once, possibly because it would in turn hurt someone else important to them, they would work with you to try to find ways to deal with at least some of the problems. Maybe he's not ever going to stop sleeping with other people, but asking to be notified when he starts seeing someone and CERTAINLY before he starts sleeping with someone is easily done and in no way is you trying to "change" him. All you're asking for is basic respect and communication.
He's being selfish, not polyamorous. The only credit I'll give him is that he has been upfront, over and over, about the fact that he ISN'T going to change and he doesn't care about your needs or feelings. That's not a relationship. That's him using you, and you need to let him know that you are no longer going to tolerate it.
Pan Female, Hinge in a V between my mono (straight) husband, Monochrome and my poly (pan) partner, ThatGuyInBlack