My ex has supervised visitation with our 18 month old. He is bipolar and not on meds.?

He also abuses drugs. He has visitation every Sat. from 10-12. He is also being very vindictive. Our mutual friend(during marriage, actually his best friend and wife) have text me that they are going to see family on Sat. and asked if they could change the day to Friday. I just think he has other plans. Shouldn't he of asked? Then, out of desperation he he texts me if we can change it to Fri. I tell him how about Wens.? He texts back and says how about early Sat. morning? I say, "I thought your friends were visiting family?" He says," at noon. " I say, "The earliest I can do it is 9:30." He texts me and says,"Nevermind. his friends are actually leaving at 5a.m." Then, threatens me, "I guess you won't get your child support check." Then 2 hrs. later tells me, "Ok, I can do it on Wens." My question is if your were me would you let him change it to Wens. after all that bs.? Or would you make him keep to his Saturday visitation? Thanks so much for your help.