@maxdancona,
I am curious... why are you focusing on the "legal custody" (you don't need to answer this if it is too personal)?
Legal custody is the least important issue in my experience. Other than deciding where my daughter will go to school (which ended up being something we agreed about), and an brief disagreement about vaccinations (where I drew the line and her mother backed down)... legal custody isn't very important.
Far more important is the amount of time you can spend being a father to your daughter. You don't have many years to build this bond. Once they become teenagers... the issue of custody becomes less and less important (my daughter now decides for herself what she wants to do with which parent).
Make sure you can have as much quality time with your daughter as you can. During this time be a father, focus on your daughter, care for her, help her, do things that she likes to do.
There isn't that much time you get raising a child. Make sure whatever happens with legal custody that you make the most of this time.