Advice on coparenting?

Going through a custody battle. And supervised visits are coming to an end. I have so much anxiety bout the children being alone with him. He had never "cared for them" it was always "my job" now were going through a divorce and he all of a sudden "knows how to parent". I just want to cry about them being alone with him. They are 4. And 1.5 yrs old. He was emotionally abusive and already telling our son secrets to not tell me. Hes not paying child support because he doesnt think he needs to. He lives in a rehab/working there so my home is the visitation place and I have having him there and I have to leave. I just need advice how you guys got through it. I know its about the children but its so much easier said than done. Im at the beginning stages. And still in a custody battle. So this is still fresh. Help?