What would you do?

So I got a divorce about a year ago... we have a child together . Well he recently got engaged and from the get go I had a nasty feeling about her. “Mother’s intuition “ anyways he has supervised visitation awarded in divorce decree. Well, he was complaining he had no time to come see his daughter (he lives in Chicago , I’m in California) well, all hell broke lose when I bought him a plane ticket but not his fiancé... she messaged me saying what I should be doing with mine and his child. I told her that what happens with my daughter is discussed with the mother and father. I don’t think she liked that very much because now I’m getting threatening messages from fake profiles and they mention things that only my ex husband knew... like connect the dots. In these messages say that someone is going to rape me and she called my daughter a whore... I know it’s her because of the things only he knew was said! This is an awful situation to be in and to top it off he blocked me from everything because I tried to bring it up to him and he said he doesn’t want to be in our daughters life. Like wtf!