I'm sorry you've found yourself in this conflict and strain, Potato.
It sounds like the limit you put on that relationship was fair given both his behavior with it and hers. It also isn't surprising that you can't get over this if he won't talk with you so the two of you can process it, and then also have talks about re-setting agreements and limits and boundaries.
How might you feel about telling him you want to move forward, but you need the two of you to really talk this out so that you can do that, telling him that's just not negotiable for you?
I want to add that it may be that in trying to make this talk happen, or in having it, you still discover you can't move forward...and maybe that's because you shouldn't. After all, it sounds like he betrayed your trust and broke and agreement behind your back. It seems he both won't let you try and talk this out and also will not take responsibility for what he's done. All of these things -- especially if he won't budge -- are indications that this may not be a good relationship for you to stay in, as they are signals the other person in this relationship isn't willing anymore to do their part in it. So, that's just something I'd start thinking about or at least preparing yourself for.
Never doubt that a small group of thoughtful, committed citizens can change the world. Indeed, it is the only thing that ever has. - Margaret Mead