kinship foster caregiver seeking guidance after being thrown in the deep end

So, a little back story... My husband and I took in my cousin's children, both boys (3 and 5 years old), under emergency conditions. They were removed from my cousin and his gf after being found wandering around alone about 16 months ago and placed with my uncle, their grandfather, through kinship care. After being found wandering again (not once but several times) while in my uncle's care a few weeks ago, they were removed again and placed in foster care. My hat was thrown in the ring somewhere along the line and when contacted I agreed to take them on a temporary basis because the situation was explained as urgent. While we were being processed the foster family requested the boys' removal and they were expedited to my home. Once in the home we were basically INFORMED that the placement was going to be permanent, not temporary, and parental rights were in the process of being terminated. I have two step-daughters, 13 and 15, on the weekends as well as to bio sons, 10 and 4, who live with us full time. My oldest son is special needs (ADHD and Autism) and I consider myself relatively well versed in coping skills and the benefits of structured environments, etc. That said, I think I am in way over my head. It has only been a week and I am becoming increasingly concerned with the situation. After speaking with the former foster parent about 4 days in, I learned that what was described by the cw as " innocent show and tell between boys" was actually several instances of sexually predatory behavior by the older child against two of their foster sons. I, too, have witnessed some questionable behavior since they have been in my care. No overt line crossing at this point, but definitely enough of a preoccupation that I noticed even before the fp had said anything--and its occurring with both boys. Both are also very aggressive towards my bio sons- physically (headbutting, punching, etc.) and psychologically (saying they hate them and that we decided to throw my boys away). In fact both of my boys have been quarantining themselves in their rooms to get away from them. Constant supervision and consistent consequences have done nothing to deter this type of behavior. My youngest keeps telling me that his heart is breaking----and that breaks my heart unlike anything I have ever experienced. Though they are clingy and overly loving when it comes to me, my husband, and our teenage girls, I am having a hard time bonding with them because of how nasty they are to my boys. I feel sympathy for my cousin's boys-I know it is trauma that I am seeing, but I just dont think this situation is going to be manageable for any length of time. My youngest especially is really suffering. He tries so hard to be kind to them and he is just crushed by how mean they are toward him. He doesnt understand. The cw said they needed structure and love--and that IS true, but I feel like I was deceived about the needs of these children. When we expressed our concerns to the cw she basically said that we had made a commitment and that we needed to stand by it for the sake of the kids. Now that she has found the "perfect adoptive option" she informed us that she is going on maternity leave and said we wouldnt be able to reach her until late january. She couldnt even provide the name of her replacement. So now it is 5 AM, and my third sleepless night in a row, and I dont know what to do. These children walked through the door demanding to call us mommy and daddy (although we had only met briefly in the past on 2 occasions), and the last thing I want to do is cause even more damage to their poor little hearts, but I know this is NOT something I was prepared to handle. So I am overwhelmed with guilt--so many different kinds of guilt--and panic, and despair. We havent been able to reach anyone (because of the holiday I assume?), but I dont know how we can go on like this. I dont even know what recourse we have since they said they were making it permanent. Shouldnt we have a say in any of this? Any recommendations/advice on the situation would be appreciated! Kinship care really seems to be this strange gray area in the foster care world and I have yet to come across a situation quite like mine.