Gaining custody of a 3yr old boy.?

PLEASE READ THIS. PLEASE. I WOULD RATHER YOU READ AND GIVE A FULL AND HONEST ANSWER, OR NOTHING AT ALL.

Thank You.

This is the situation I am in:

I met this femail who has two kids and was on the outs with her husband they had a house together and after he left things to my eyes were in disarray, ( which I understand when it comes to adultery in a relationship, theirs and both of them committed it and NO i was not the guy she had an affair with ) Me being a man thought I could help or fix it.

After he moved out, I started to come able to get a better view on what was going on, what I witnessed was hardly anything was getting done.So I made a decision to move in, only under the agreement that I would pay her 50 more than what my rent was about 500 bucks ( he stopped paying for the house, she was caring the load). I moved in, am started the clean up, "trying to bring some order to the situation, from the house to her and then the kids" It all backed fired, the kids looked at me as if I was trying to run things, "well to my eyes" I was not. I understand, they were going thru changes as well, which I understood.

Now to make this long story short, after about 2yrs of complaining to her that they all, including her needed to make a continuous discussion to pitch in, finally I just stopped doing things, no more cooking all the time, no more washing there clothing, no more asking to turn off the lights, "matter of fact I separated my monies from the electricity bill, because the mother was not seeing this as a problem, yet she complained about the bill. Pretty much I just stopped doing things, she slowly but surely started to get the picture.

When we first met I told her that I can tolerate mostly anything, but would not tolerate lying when it came to other men, She lied, I started adjusting my feelings for her but stayed. Mainly because we have a child together and I wanted to work it out.

That passed and the relationship has been up and down, mostly down, shaky. She comes to me 3 weeks ago and told me a friend of hers texted her, which I was cool with, she said he was married, I was ok with that to but I wanted to know if his wife knew that he was texting, she did not know, but she said that they were all friends. My suggestion was for us all to meet, and discuss this, she flat out refuse to do that. That put me here to you guys.

She wants me out and child support, I just got layed off but have a good prospect for a new job. I dont have much money I just got our taxes, about 2500, she wants me to pay rent and child care until I move out (which I understand) but by doing this will exhaust what little I have, when she could allow me to get my place and get set up, like she did with her husband. She makes about 55k and she is getting child support for her 2 daughters. Finally fully seeing the degree of unfairness she is going to I said to her that once I get set on my feet and my own place I was going to get full of the boy, she all but laughed at it.

What are the chances of me gaining full custody of the boy?