Paragraph breaks would help -- just a thought.
I am sorry you hurt.
Since he is willing to end it and not pursue poly relationships at this time, why are you NOT willing to take him up on it? What are you getting out of this continuing?
I feel like every time I talk to him my emotions and fears start snowballing out control and he gets frustrated saying that I am overwhelming him and making him feel bad. Once I start talking I feel I cant stop without bottling up emotions (which i have read you are not suppose to do in poly relationships). I don't know how to tell him just a little about what I am feeling with out revealing the level of my hurt.
Why not take the time out to strengthen how you and he communicate with each other and deal with strong emotions? BOTH of you sound like you are emotionally flooding
He doesn't have to break up with her, if that is not what is wanted, but you guys could take a time out to focus on THIS issue in THIS relationship.
Does this resonate? Can you as a couple do more page 5 and 6 things?
Do you have before care and after care things you do before and after his dates? To reassure and reconnect? Is the pace of his other relationship just moving too fast for you to take on board and still feel safe/respected in your relationship with him?