What you are dreaming is natural. You are working through your feelings and desires in the safety of a dream. But dreams being dreams dont work out the way real life does and her not fighting back is possibly your worst nightmare- that you are attacking her and she is in the right. BUT it is JUST a dream and so you can take from it what you need.
If it were my dream, I would think:
I am angry with her (she is instrumental in the breakdown of my relationship)
I want to hit her (ditto)
If I do hit her (in RL) that would make me a bad person (mind showing you the consequences of flying off the handle- reminding you NOT to hit her in RL)
She does not fight back- if I hit her there will be consequences because SHE did not start it (he did)
I am 16 years on from a split that sounds very similar and I still have those dreams. I also have dreams that we (me and her) are about to become friends but I always want to do something (hit her, spit at her, remember who the hell she is) in time to stop me. When I wake up I am so relieved to remember that it was all in the past and I did not hit her or make friends with her.
Dreams are great. Get a good dreamwork analysis book and write your dreams down. Write in the present tense (I am about to hit her... I feel... etc) and then having written all you can remembe: Reflect on what messages are coming out from them. Often they will be more obvious than you think... if she wont hit back- is that linked to a message you were given as a child "dont hit back"... or "turn the other cheek", these kinds of messages are played out in technicolor in dreams. In dreams you play all the roles- so even she is you (I know, it is horrid to imagine that) and what she does is what you might be inclined to do in that situation.
I will go and find my dreamwork books and see if I can find the best title for you if you want to have a go at a fuller analysis? Dont read dreambooks that are dictionaries of symbols- your symbols are your own and they are unique to you. It takes time to discover what your dream world is telling you but it is worth listening to.
I am so sorry for you to be going through this, it is hell. It will get better. Even the baby stuff will get better, especially if you keep your distance. You will be able to go out and have fun and they will be stuck at home with a baby. You will always be further on than they are. Be smug in that :)