I'm currently in a custody battle with the mother of my niece and nephew? Updated info?

To make the story short and simple....I have temp custody of my 2 year old niece and 3 year old nephew notarized by a judge since 2009, but I actually I have these children under my care since my niece was 2 weeks old and nephew was 5 month old. Their biological mother hasn't been in the children lives, but in some occasions "I'LL GET TO THAT IN A SECOND". She doesn't call or checked for the children. My husband and I have provided the children with food, clothing, shelter and the love of a parent. The mother has been collecting the children welfare and WIC benefits for the past years. The children are being raised at my resident along with my soon to be 2 years old son, theres a big bond among this children. I have a 4 bedroom resident and each child have the own separate bedroom with a bed, toys etc. DYFS had came a couple of times to visit and check the children welfare and they were surprised on how this children are living under my care. Like I said previously, The only times the mother came to see the children is when we have a family reunion or any activities like birthday parties etc. other times were when DYFS were called on her and at one occasion in 2010, she took my nephew for two weeks and during that time he became very sick and she ignored the situation, my mother which is their grandmother took action of the situation and took him to the hospital where he ended up diagnosed with MERSA and a cyst with fluids in his left lung. I became aware of the situation after he was admitted. After he recuperated, I took him back home with me. Now, after all this time of me being the legal custodian of the children, the mother wants to regain custody of the children. The reason she wants custody back of the children is because she has a case dealing with her other 3 children of child endangerment. She left her other 3 children in the care of a man that is mentally unstable and was drunk at the time while she went to a bar to buy liquor. The man threatened the children to cut off their toes and fingers and actually cut himself to show them he wasn't playing. I believe in my understanding that she wants to regain custody of the children back, because she knows she's committing welfare fraud and she's afraid of getting caught. We've been through a seminar and not to long ago we were at a mediation to work out a deal but she refused my proposal because she wants full residential custody of the children. We're schedule for a hearing in front of a judge on May 17, so my questions are....What's my chances of wining this hearing and continuing being these children legal guardian?...I'm aware of her having the upper hand because she's the biological mother and the judge might favor her in that way, but would a judge waive that reason and favor me as the psychological parent?.....Would the child endangerment case dealing with her other 3 children would benefit us and increase my chances of winning the custody hearing?......other notes: The mediator told me that the judge might treat me as the father not as a third party of the children....I'm considered the psychological parent of the children....the children are in a save environment in my resident.....I do have an attorney and he said that I have a strong chance of continuing the temp custody.....the biological mother has a long history with CPS.....all of the children medical history such as shots, appointments etc. has my signature