How to deal with a jerk of an ex ..

My ex was a jerk. He hardly worked to help provide for our 2 kids and even when he held a job more than a month he never contributed to bills or food. Since we’ve been separated (3 months) he has just finally provided some help and did some grocery shopping for us, only to throw it in my face and act like he is almighty because he provided for the first time, he even came to drop the food off and tried to cause a scene about it. I cannot deal with this man any longer, I can’t understand how his mind works and I honestly don’t want anything to do with him at all. How do I deal with an ex like this!