Life is a mess

I really need some help and I don't know what to do any more since I'm so numb and trying to deal with soooooo much stuff all at once. So here is a little bit of information and I'm sorry if its so long as well.
First I'm trying to deal with a car accident I had with my children in the car. We all walked out fine, just a tad sore. Enough to scare the crap out of us all. I was pushed off the road. If my car had of hit the other car it would of hit my son and he wouldn't be here today. Thank god that never happened and I was able to miss the car in front of us. As we were off the road in bush was the scary part as I couldn't see a thing and had no idea if we were going to hit anything as it was full of trees. Lucky we didn't hit anything else. We came close to hitting a tree because as I opened my door, the door hit the tree. I'm in counselling to help with the nightmares and to help me through it and to try and get rid of the mothers guilt. After the accident my kids went off with their grandparents. While away no one talked to them about the accident and just left it be so the kids weren't able to let it out. My son has come home even worse. Not sleeping at night and always crying about it. He is having anxiety about getting the car back and I've told the kids that when the car comes back we will take it nice and slow to get back into it. He is going to counselling as well. I just don't know what else to do to help him. Its killing me inside to see him like this. I have guilt by letting them go after what had happened but I thought they would be ok since it was grandparents and they would help them through it. I feel like I have let my kids down by letting them go and a whole heap of other feelings that I know I shouldn't be feeling as I know I did everything I could to save the kids and myself. My head is still all over the place about it all.
On top of all that, my partner is in the middle of a custody case over his children. His ex has made up all these lies about him. They had shared 50/50 care of the children. One week with us and one week with their mother. We have found out that the oldest child has been helping her mother out and telling her everything that happens in our house and also making up lies about how the father is towards the kids. Because of the lies, the mother came over to our place while she known my partner was out. The ex and her partner told the kids to get in the car and then asked me over to the car. She then tried to tell me that my partner is cheating on me and that I need to go through his phone to find out the truth. I didn't get into it with her as all of our children where standing around hearing it all. The fact is that the ex has told the daughter to snoop through her fathers phone and to give her all the information so she can let me know since she is calming he did it to her. Which I know for a fact that never happened. The ex also called the police to find out if she would get in trouble by just taking the kids. We all thought there was no order in place but as we found out that there is an order in place and if she doesn't return the kids on Monday then we can do something about it. I'm more worried about the children as they were just ripped out of our house without even knowing why. The ex is also not letting us see the children or even talk to them on the phone and keeps saying they are too scared of their dad. Which I know is bs because I know those kids love their father. I also know for a fact that she isn't letting the kids go to school incase we go and take them back. All in all its the kids that are missing out and so confused on what the hell is going on. The oldest child moved back in the mother yesterday as well.
I'm trying so hard to be the strong one for my partner as he feels like he has lost everything as he is the one that has had the child since the marriage broke up. The two younger children chose to live with the father and the mother was happy to have them every second weekend until I came into the picture and since I've been here that when she went back to court to get the kids full time and make up lies to make my partner look a monster. Which he is nothing like she has painted him out to be because if he was I sure as hell wouldn't be here still and I would be on the ex's side trying to get the kids away from him. He is the most wonderful father and that's the first reason I fell in love with him. The way he took care of those kids and did everything he could to give them everything.
I just don't know how to cope any more because I'm trying to keep the rest of us together and I know my partner is going through hell at the moment. I can only imagine how he feels because I feel just half of what he feels. I just don't know how to help and I feel like its my fault the kids are gone because I didn't fight hard enough to keep them here until my partner came home. I feel like him and his family are blaming it all on me, if I had of stood up more the kids would still be with us.
Has anyone else gone through this and how did you cope? I feel like nothing I do is enough or helps my partner.