How to tell a Cancer ex to #1 off

Hi guys first post but long time lurker. Love this forum btw.
Need advice on how tell my cancer male ex,and father of my son, to piss off.
Me- female cap; sag rising and taurus moon.
Him- cancer male...dont know and don't care about the rest of his placing.
As far as our son goes, he does NOT co-parent at all. Pretty much does so when he wants to. I don't tolerate it.At the same time,Im not dwelling on it because I make sure I do what I need to for my son irregardless,so he's never lacking. I do not restrict contact or anything between them because when my son gets older, I know that his bluntly honest sag self will tell his "dad" to f off. It's their relationship,or lack thereof, so I leave it up to my son.
As far as me and the ex,goes there is no me and the ex. I sent a letter of closure on fb a couple of months ago, told him I was done with the anger and all that. That I might love him in some way and always will but I'm ready to be happy and choose to not act on those feelings anymore. It was closure for ME nothing more. I also told him he can contact and see his son whenever(something I never restricted). He responded in so many words with a whatever. Fast forward to last month, my son's grandma(the exes mom) kept my son for a memorial day weekend and also helped get me furniture. I recently had to give away my old furniture because it all wouldn't fit in my new apartment. Well fast forward again (yes alot of time travel in this one) to the day after Father's day...he calls. By this time I feel like we shouldn't even talk polite. Especially after his response to my message. It's not that I was expecting a mature response,im a Capricorn.When we express ourselves completely and you pay us in dust, pride kicks in and we expect you to keep that attitude while we move it along. Well he doesnt keep that attitude he starts with "hey what's up". And actually waits for a response. I figured I would get asked to talk to our son right away. Then he proceeds to talk my son and during the convo(on speaker btw, I just left the mall after getting this galaxy and I didnt know all the controls so couldn't have my son figure it out and end up pressing something else), I tell my son to tell his dad " happy early bday. Just to let them have something to talk about. NOTHING more. Im listening and it seemed like he was shocked thay I remembered and was thoughtful enough to pass it along. Keep in mind I refused to remind my son to tell him happy Fathers day cus th

That would be giving credit where it surely is not due.he then tells my son to hand the phone over to me. I try to put the headphones on but they werent working. I tell why I cant get my phone to work properly and he responds with some like "its ok you'll get yourself together" WTF!!! says he will call back later. He does and proceeds with the call intro before. I told him we were in hayward with a friend. He couldn't talk to his son right away because he was acting up but I had this strsnge feeling that he wad listening to my surroundings besides his son acting up. He talks our son tgen has him hand over the phoe. Then he asks me about something personal and how it's going. Im taken back because I don't want to converse about anything besides my son. So all this was bothering me for a number of reasons:
1) I don't take kindly to patronizing. You showed me how you felt about me before. No need to say supportive crap or anything positive. It seems fake as hell.
2) niceties are not needed at this point. Im completely fine with not talking unlesd we are talking about my son
3)He's done this before!! Pays me in dust, then disappears, then talks to his mom about me (oh yes he does) then when it seems favorable I.e. I look good, I could care less about talking about him to her. He goes in for the kill.
This last thing has really been bothering me because of my Cap and Sag influences. Im done and want my freedom from that aspect of our necessary relationship and I want my freedom. Im supposed to give up my freedom from him because HEwants to get in where he fits in. F NO. Everybody knows sag and sag rising will fight to the death for their freedom. Caps are free spirits on the low too and that's part of me that I don't want him to have accesd to anymore. How doI tell him to shoo away and lets stick to the task at hand

Pretty simple... "Shoo and stick to the task at hand." It's up to you not to stray from that. You need "shoo off" to mean "shoo off" or there will always be a back and fourth game of BS.