My ex is messeaging our 8 year old through XBOX

Okay some back story, my ex of 10 became addicted to meth/mostlyVerballyabusive/unfaithful and i left with my son to keep protect ourselves and so we could have a better life. I left when he was 2 and my ex would pop in when he felt like it/needed money for 2 years. (He ended up homeless) he eventually stopped. We invited him to bdays, school events etc. No show. Fast foward my son is now 8 years old. About 6 months ago he messaged me out of nowhere saying he wanted to take our sob ON HIS OWN. I said no cuz he doesnt know you and i need to know you are sober. So lets start with supervised and move up. He refused and threatened court. So i filed. The mediator suggested supervised visits at a facility and to pass a drug test. He missed all court dates. And all drug tests. They gave him 5 chances to test. Sent me a rude ass “goodbye message” about how i ruied his life and took his son and blocked me on everything. Now he found my son on his XBOX. yes you read that right. And is messaging him there. Again our child is 8. I find this inappropriate… im attaching some photos of the message. Should i just monitor thw conversations or should i tell my ex this is strange??