Get TOUGH!
I was in the very same situation as you are and I cannot stress, emphasize, or provide enough examples of how much abuse he is STILL wielding, even now. I apologize, in advance, for the length of my response.
In the case of any abusive narcissist, take NOTHING that he promises as Truth. The first thing you need to do is to hire the best attorney that you can find that specializes in abuse. Whether the abusive NPD can afford anything or not isn't your problem - the Court will see to it that he either works his BUTT off to support his offspring (and, you), or whether he will be staring at some time in the County Jail. He might also be ordered to pay for counseling, your legal fees, etc., so take off your gloves, narrow your eyes, and prepare for battle - it's no joke. An abusive narcissist will do anything and everything that they can to manipulate friends, family, supervisors, YOUR boss and co-workers, Court ordered counselors, judges, attorneys, etc. This will take every ounce of courage that you have. Do it for your Self (your Life's Spark) and for your children. Do not move another step forward with your emotions on your sleeves - there is no reasoning with an abusive NPD. There is no closure with an abusive NPD. There is no negotiating with an abusive NPD. There are only endless mind games, manipulations, abuse, and insanity, especially for the children involved. Seek SUPERVISED visitation ONLY - in that way, he will not be alone with the children to fill their heads with abusive garbage. Your emotions will be his first point of attack, always, "you don't deserve the children because you were never a good parent.: Or, "You don't even have a full-time job! You'll NEVER make it without me!" Or, "The kids know that you're a lesbian and the court will never let a lesbian take MY kids!" ETC. Be prepared and offer no reaction. Everything that issues forth from his mouth is FALSE.
Also, it will be more than beneficial for you to enter into counseling (and, make HIM pay for it) with a specialist in domestic violence and abuse - the counselor will recognize the abuse and help you to work through and away from it. The counselor will also be able to document all of this. For God's sake, HOLD NOTHING BACK - whether it is sexual, financial, verbal, physical, spiritual, or emotional, please lay it all out on the table. That was one of my mistakes - I was so embarassed that I had allowed myself to become a victim of an abusive NPD that I just refused to say, "My husband often raped me and dared me to file charges of spousal rape." I was too ashamed to say, "My husband, whom I trusted, would tell me that I didn't earn the money, therefore, I had no need to be involved in our financial business." I was too naive of abuse to say, "My husband told me that practicing my religion was 'bogus' and that I had to convert to HIS choice of religion if I wanted to take our children to church." I couldn't admit that our "horseplay" which happened often in front of our children was so painful that my extremeties would sometimes be rendered completely useless for an hour (or, more). I couldn't tell a soul that my husband would threaten to shoot our children, then me, then himself - in front of our children - as a method of ultimate control: whatever he wanted to diffuse his suicidal threats, I would do.
Today, I can (and, do) tell anyone what happened and what I was a victim to. I can also tell them how insidious abuse is - you can't see it coming because the victims' self-esteem and sanity is slowly, but surely, dismembered over months and years. This is why it is so imperative that human beings understand the cycle and dynamics of abuse AND the ploys of narcissism!
Start documenting every conversation, every action, everything that the children say. Note dates, times, exact quotes, and exact responses with NO emotional input or embellishments. You must do this even if it means that you might not look so great, either - by the time we're ready to leave, the abusive narcissist has forced us to engage in some activities that we would rather have not been involved in (at the very least), so get a stiff upper lip and say to your Self, "Okay. I'm going to be OKAY, regardless of what I've been a party to and what I have endured. I am GOING to Survive!"
#90837, you are welcome to email me, if you wish - I may be slow in responding in the next few days, but I've been in your shoes. Molly Bloom has been where you are, as well - she is a very wise, strong, and supportive human being. There are many, MANY other human beings here, at Curezone.com, who have Survived their abusive and NPD relationships whether it was with a spouse, partner, parent, supervisor, etc. They will be more than willing to help you whenever you feel the need for it.
God bless you on your path to Healing.