Coming from someone who has been in that situation I will say this.

First QD's advice was dead on, the only way to truly get full custody is to prove her unfit which is damn near impossible if she doesnt have a criminal record and works a regular job.

Second I think the emotion of the situation is blinding you from what is really important..the child. Child support isnt a chore, it is a responsibility.

I will say if you really want the situation to come out the best it can for everyone develop a good relationship with the mother. Obviously you wont be dating but communicate on a regular basis, it will keep her from being on the defensive and having no mercy on you because honestly the ball is in her court and will be till the child is a teenager.

If you want custody file for joint physical custody, the judge will look at you like an ass for wanting to take the child away from his or her mother. With joint physical custody you acknowledge that the child needs his or her mother just as much as they need you, you get to see your child on a regular basis and I believe child support is significantly less since you have him or her just as much as the mother. Even if you are not granted this at first keep working at it, keep receipts and a journal.. if you have your own place have a room set aside for the child.

With my situation we never even went to court because I put the petty sh*t between me and her aside and did what is best for our son. Any time my son needs something he has it and then some.. when I'm not working I have him with me so she has time to herself, for most women that is all they want if they are not bitter.

Imagine what your child would think if they heard you say you will not pay for anything that is not in your possession. The situation may be f*cked up now but if you just continue to be a good father then the reward will come in due time.