Ex partner woes

Hi ladies and gents, I have a question, I apologize for the length but I need to get this off my chest!

I'm so done with my child's father, we have been separated since his birth, four years ago, we had a five year toxic relationship, I was very young when we got together, we broke up so many times but he would always pull me back in. He has bipolar and depression, and was hospitalised and put into mental facilities during our relationship, I found out I was pregnant and had to go tell him while he was in care.. Our relationahip ended when I was nine months pregnant and he got drunk, verbally abusing me, and eventually pushing me over, I had had enough, I wanted more for my baby and I left, I went into labor the next day (because of stress) and had a terrible 37 hour labor. At first he took our baby and was very helpful and supportive, until I told him that it didn't matter, I wasn't coming back with him, for a while we Co parented pretty well, we had a private agreement for child support and I neievely thought it would stay that way. Fast forward four years, we have both moved on, had children with other people, I have been with my partner with three years and he had a baby with a women who need up leaving him and their child for hardcore drugs (or so I am told, but whatever the case he has full custody). But unfortunately as much as I try he will not Co parent. I'm so sick of waking up to abusive Facebook msgs(I refuse to let him have my phone number because I've had to change it from him blowing up my phone at 1 or 2 in the morning, I'm talking 20 texts and 10 missed calls in an hour), I usually ignore him for a couple of days then text him asking for an apology and everything gets "smoothed over". If he doesn't get anything his way, this week it was me telling him he needed to come pick up his son if he wanted him because I had no fuel and didn't get paid for a few days, which ended in him sending me a three page msg on our Skype(which was on my sons iPad, so he could FaceTime with his dad) saying terrible mean things, that our son hated me, that he never wanted to see him again because I "make it so hard" that he was going to spend all his money on his other child and my son can get f'ed , he mocked that we struggle with money (my husband works hard so I can stay home with our kids, while my ex gets single parenting payments and lives with his mother and pays 15 child support a month), he even try's to get my partner and I to fight by sending me photos of his genitalia by "accident"!! I have also received msg from a fake account that I assume is him or a friend of, stating that if I don't "correct" the situation there will be consequences, I've blocked that account straight away though. This happens at least once a month, I'm so sick of it. I'm so sick of his little games and I wish he could just put our son first and not have this need to try and play him against me. He isn't consistent with visitation and only wants things his way, we tried mediation (set up by me) but it didn't work, we hadn't spoken in six months at that point, so it was calm and more about his exs drug use then his issues. I really just want to block all contact (since his first sentence in the last msg I got was that he is never seeing his son again) and let him sort out mediation if he wants to see his son, I feel like I've gone above and beyond (taking my child to see him, gone out of my way to encourage their relationship and never spoken Ill of his father) and it keeps getting thrown in my face. I'm at my breaking point, but I don't want to block it all off and then get told I'm getting in trouble for "keeping them apart". How do approach this situation? Can I stop all contact just because of abusive text msg? How many times can I get called names! How is he allowed to abuse me and I just have to deal with it?