What Should I Do Next..Tired of Lies

What is the name of your state? Maryland
Some of you may remember my situation. I sent son's dad a certified letter because he did not contact me or show for scheduled visitation. I sent it because everytime a child support issue arise, he say he going to have me locked up for contempt of the order. He does not utilize, but blames me. I sent the certified letter off last Monday, since he did not pick son up for visitation Thursday and Friday of the previous week. Son also informed him he has his own phone to reach him on since he lie and say I don't allow him to call him. It has been two weeks and dad has not returned son's call. Son and I saw dad at aunt's house Saturday. We spoke to him and he did not speak. He turned his nose up at both of us. I heard him telling his aunt in another room that I just want his money. He was ordered to pay $100 a month 8 years ago and asking for a little more money is not being greedy. The child is 8 years older now. I heard him tell his aunt he don't have any more money to give, but he has another child on way that will be born in October or November. He has not told his family or our son about the other child. My knows about the child, but he was not the one who told him. His grandmother told me that dad arrived in North Carolina at 6:30 p.m. the Friday he was supposed to get son and left to come back to Maryland Sunday night. He was also supposed to take son down there, but like I said he did not show. This Thursday and Friday is his week for visitation. What should I do? Would it be appropriate to give a courtesy call today reminding him that this is his week and call me on Wednesday with a pick up time. Should I just not do anything because just like I am keeping track of the weeks so should he. If he doesn't show, would it be appropriate to send another letter informing him that he failed to contact me in reference to visitation. I don't want him to keep blaming me for his no shows. Son also saw dad at aunt's house, and dad did not speak to son either. Should I keep sending him a letter when he miss to cover my butt, or what? Thanks for any advice. Sorry to bother you all.