terminate bio dad's rights by agreement for abuse

My sister has sole legal and physical custody of her 2 kids, with bio dad having hit/miss visitation (by his choice). All live in Mississippi. Learned bio dad abusing kids, filed suit to terminate parental rights, gathered mountains of credible and disturbing evidence, including finding of DHS of bio dad's abuse of his kids, and findings of his abuse of other kids. On eve of bio dad's deposition, he said he was afraid he would commit perjury, did not want evidence to come out, and would sign anything put in front of him to terminate his rights, as long as suit dropped. Both attorneys went before judge to terminate rights, but judge hesitant because sister not about to remarry. (Sister has very supportive family, however). Judge also said termination statute(15-103) not applicable because kids not "removed from home" of abusive father--already with mother. Judge said just to drop suit, father agree to not get the kids, sister send child support payment back to father. Nothing in writing, father has history of deceit and fraud, and nothing to protect sister and kids in the future, as her suit becomes stale. Also, if anything ever happened to sister, kids likely go to abusive bio dad. Any ideas of caselaw or otherwise to take to judge to convince him statute applies (judge said he is open) and/or to protect sister and kids in the future?