End of my tether

Hi.I am split up from my kids dad (5 years), after he was emotionally and physically abusive in our relationship.I have never stopped him seeing our children since this...and he has them every weekend sat overnight and Sunday and also picks them up once a week on a weekday for a club they go to.The last year as they have got older he has started insulting them whenever he sees them...not good enough this, not good enough at that. He told one of them he was overweight (he isn't) and if he grew his hair out he would not be taken seriously.In the last school holiday they went on holiday with his family for the week. When the next weekend came they said they wanted to stay with me as they hadn't seen me. I said that was fine- let their dad know and he went insane at me calling me names saying I was trying to turn them against him???He picked them up this week for dinner one night and they said see you this weekend. He turned round and told them he was now busy for two weeks and if they wanted to really see him they would have gone last weekend.This turned into a row on fathers day of me trying to encourage them to go and him sitting in the car outside refusing to come in and say anything. Apparently they should have come out and respect the fact that as an adult he is allowed to change his mind if he wants to see them.I raise them quite liberally and there isn't a chance I am forcing them out of the door to do something they don't want to do.He is now posting pictures up saying child abuse is not letting kids see their dad....he has both their mobiles, my house phone number which has a specific ring when he calls so they can answer...has had them every weekend for the last 4 yeaRs and takes them out once a week.He can't seem to fathom as he never has that this is his fault for the way he has spopen and treated them.Any suggestions where I can go from here? He has said he's an adult and they are children so they should be doing what he says and if I don't back him entirely or have go at hI'm about upsetting them that this means I'm teaching them to disrespect him and therefore it is my fault they don't want to come. via /r/Parenting https://ift.tt/2JWaqN0