Going without an attorney, I'd say slim to none. You need an advocate to reverse the damage already done and put him in the lime light, not your past behavior. If you seriously want the child, you need to hire an attorney to make sure your chances are the best possible. You are in a tough spot and need to dig yourself out. Good luck.
Disclaimer: This answer is intended for informational and educational purposes only and should not be considered legal advice nor forming the attorney client relationship.
Without an attorney, you are not going to get what you want. Even with one, you may have insurmountable problems.
When he assaulted you, did you make police reports? If so, was he ever convicted for family violence? If he has been convicted of family violence during the past two years, he has no great story to tell either.
There are a range of possible outcomes in your case: If you are compliant with your psychiatric care program, you have a chance for joint managing conservatorship, but with a conviction for family violence, you are not likely to be the primary conservator.
I am so sorry that you are going through all this. Please try to get an attorney. Call Legal Aid. Call the Texas Legal Services Center (www.tlsc.org). Borrow money, get a second job--do what you have to do but please do not make things worse by representing yourself.