After a months-long hiatus, I need help!

Things have been mostly good skid-wise: SS13 has been a stage 5 clinger to my SO, which is weird. The kid turned 13 and all of a sudden he is in the living room just wanting to watch TV with my SO constantly. He's always touching him or hanging on him. Shouldn't he be hiding out or something?? SD10 has been mostly great as usual. Crazy (BM) was leaving us alone (ish), but then my SO and I bought a house, plus she was able to file for 50/50 custody in August, so we were just waiting for her to lose her mind about all of that, and she did not disappoint. To recap, my SO has majority custody, 67%, and during the school year we have them 10 days in a row. She gets two 4-day wknds a month. Because she is crazy, and wouldn't hold a job or keep an apt. But in the past 2 years, she has had a job and an apt. Long story short, she sent my SO a message on Our Family Wizard last month, first asking for 50/50 custody (he said no), and that's when the wheels fell off the bus. She replied calling me names, telling him he's a terrible father, how could he do this to her,  "I am their mother", blah blah blah, and that our new house isn't his and his parents co-signed (the mortgage is in my name only) and gave him a down-payment (they're giving us a down-payment??? I had no idea!!!  *yahoo*  ) and he should stop lying to everyone. After that it was multiple messages a day about ridiculous things, petty accusations saying we forced SD to go on a roller-coaster, we don't carry her defibrillator, we don't have food in the house (we could survive an apocalypse quite comfortably for several months), she spent $250 on school supplies and we needed to buy the backpacks, shoes, and all the clothes. It went on and on.

Then she files for 50/50 custody.

A week later, she calls CPS on both us and herself "anonymously". So CPS shows up at her house to talk about the BS concerns she had made up for her house, and she tries to tell skids that it must have been us that called. Nice try, because then they call my SO and the complaints they received about us were these: 1) We forced SD to go on a roller-coaster. 2) We don't carry the defibrillator. 3) We don't have food in the house.  Being the crack team of investigators we are, we quickly determine it was Crazy that called. My SO tells CPS that she had just filed for 50/50 custody, and that he has proof of all of these accusations on OFW, which she has repeatedly messaged to us. They find this interesting since she had failed to mention this when she talked to them, and pretty sure Crazy is now the absolute dumbest person in the world if she thought no one would figure out it was her that called. So yesterday, I got to spend 30 minutes on the phone with CPS discussing this. She asked if my SO and I have any "stressors" in our life, and I said, This. THIS is our stressor. We are beaten down and exhausted from her. I'm not the kind of person to have CPS called on me. I don't hurt the kids, and my SO is more on the Disney Dad end of the spectrum than anything. For those that always say "ignore her", I don't get to ignore this.

Here's the kicker though. He was planning to fight her on the custody thing to try and retain the 67% he has. Not with a lawyer this time because we didn't have high hopes that he would win, because although her crazy is in full-effect, she can provide for their basic needs which is all that really seems to matter these days.  We didn't want to go back in debt with a lawyer when we are pretty sure she will win. They have mediation in 10 days to try and come to an agreement. But now he is so worn out and exhausted from all of her constant BS and the CPS call, that he has decided to agree to 50/50.  *shok*   I am super torn about this, because I do believe they're better off with us, but I am also exhausted with her nonsense, and things are just so much easier when they're not here. Less fights, less stress. I have my alone time. Selfish, yes. But I was on board to try and keep the custody we had as well, it just wasn't going to happen. Not gonna lie though, secretly excited about more skid-free time, especially in our new house that we LOVE. And the kids want 50/50 anyway, so f*ck it. We're done fighting it.  

Here's where I need help: We thought if he agrees to 50/50 in mediation, this would be a good time to get her to agree to some things as well. This constant communication and nonsense from her HAS to stop. I don't know how much good it will actually do, but I think it would be worth a shot to try and firm up the CO in regards to rules of communication on OFW, rules of who pays for what, etc. Right now, she messages constantly, constant name-calling of me, my SO, accusations.  She thinks she should only have to pay for the school supplies (pens, paper, etc), and we should buy backpacks, gym shoes, school shoes, clothes, and pay for ALL field trips, plus my SO pays for private school for skids (that is in the agreement). Next year SS will be going to public high school.  Maybe he can ask that she pay for that, plus any field trip costs for him?

Has anyone dealt with this before? Any suggestions on rules for communicating on the app?