Can I use this in a custody case?

My baby dad is a deadbeat and was abusive to me. He hasn’t shown any interest in our 2 kids in a month. I posted a video of my son playing in the store and one of his friends commented something sarcastic about my parenting. So I made a comment back, mentioning that my baby dad was a deadbeat. Well his mom (who is also a deadbeat) took it upon herself to write a paragraph of a response, claiming that I was “trying to trap him” (because he didn’t want to use protection or pull out during the whole relationship so I took pregnancy tests because I was scared I’d end up with a third by him), that he kicked me out because I “didn’t work” (he was controlling and didn’t want me to. (I also have proof that I was trying. I also wasn’t really cleared to work at the time because of how newly postpartum I was), how I withhold the kids from him because I want to have sex with him (which is… wild). etc. and then also messaged me calling me a bunch of gross names and continuing on with the same made up “you’re a bad mom” bullshit she said in her comment. But in messages, she also threatened that if I “keep it up”, they’re gonna for custody. So clearly they’re not worried about custody because they genuinely care, it’d just be a way of punishment in their eyes. I deleted her comment and blocked her on messenger but it glitched and wouldn’t block her Facebook. So she tagged me in a post that was a screenshot of the comment saying “what’s wrong you don’t want people knowing “the truth”?”

I just want to be done. I want my kids to be safe. But instead now they’re just the next pawns in this weird ass game. For +4 years, I put up with abuse from them. I know I shouldn’t have said anything but I just get tired of taking care of them alone and then everything falling back on me while they don’t even bat an eye at him. I’ve deleted and blocked them all