I have sole legal and physical custody of my 3 boys
Their dad sees them usually about 3 hours a month but the last few visits have been awful for them. My 9year old has anxiety and sees a counselor every other week and a psych doctor and they believe a lot of the anxiety is related to his father. Last month he took them to a movie and picked my 9year old up by his shirt and was screaming at him. This weekend they went with him to a wedding and my 9 year old fell and hurt himself and he made him sit down for over a hour and wouldn't let him clean up his leg or get him a band aid and recorded him crying and made hm sit there and watch it over and over again. My 10 year old also told me be accidently called his dad Adam (my bf of 4 years that the kids are with daily) and he made them sit and say dad over and over again for a hour. He also smacked my 6 year old in the chest this weekend for laughing when his brit her stepped on a cup. I do not hit or touch my kids they have timeouts on occasion but they are good kids. We have no visitation set up how or should I motion for no visits or supervised? He currently has supervised visits with his daughter and does not see his other daughter. In November I have text from him telling me to come pick them up because he wasn't feeding them it was 4pm Sunday and he had them since Friday. They had told me he only made chili on Friday night and they ate cheese and copied Saturday so I hadnt let him have them since then
Im at my wit's end with him and the boys don't want to go with him and we have no communication because he either threatens gp take them or its and argument. He has never once did anything for then such as sports events taking them to school picking them up from school all 3 are healthy good kids with perfect attendance and I'm worried what will happen if they continue to go with him! He has sent messages saying he was going to kill himself and telling the boys he would kill me so they have to live with him and be "normal" I'm just done putting my kids through the torture I need to know the next step on hoe to stop him from seeing them.

First off: I hope you are saving all of the text messages where he is saying he is going to kill himself. You can certainly use them against him (proof of mental stability) if he every tries to fight you for custody/visitation. Secondly if you have no court ordered visitation set up you have every right to stop him from taking them if you feel it is not in their best interest. Granted I believe that kids should have both parents in their life's but if they are inflecting physical or emotional abuse they need to have limited access to the kids. Is there anyway you can get proof of the things the kids are telling you have happened? Someone you know and trust that was at the wedding and saw what happened. Anyone at the theater that saw what he did? Or any witnesses to anything else?