@SpinningFloppa if you are ok with 'hosting' responses to PP on your thread, as you both have the much the same issue ...?
@Username112233 cheers - the ballsy-ness grew with age & experience.
All you have to do is practice it, & you'll get ballsy too!
I suspect your main problem here isn't so much your ex, as your own hesitant approach to dealing with him. You are anticipating pushback, anger, resistance ... almost as if YOU need HIS permission to make a simple decision!
This is not a criticism btw - please don't feel I am viewing you negatively in the least I admire you for wanting to make this stand & want to see you not just achieve it, but gain confidence through doing it.
It's very simple. Not easy ... that comes with time & practice - but the thing is to view it as simple, & not allow him to complicate it by DARVO'ing you or coming up with his own reasons why he ought to still be having contact at your home.
Message him "as discussed, it's no longer appropriate for you to have contact at my home, so from [date of next pick up] you will need to either take son out, or have him at your mum's."
No more than that. Simplicity - remember?
No "please", no "would you mind" - this is an instruction, not a request.
When his inevitable objections start - use the Broken Record technique.
www.revolutionlearning.co.uk/article/the-broken-record-technique/
"This is not up for discussion, you are no longer having contact in my home"
Remember that you do not OWE him a response.
If he gets arsey, or inundates you with messages - ignore him.
Conduct yourself like a woman who expects to be heard.
Does he have a key to your home?
You might find it easier to change the locks than ask for your key back. Asking him for it gives him too much ammunition for playing silly buggers with. Also - your aim is to reduce comms with him, not to set yourself up for more back & forth from him.
Once you've changed the locks - he can no longer enter your home, so job done & you are no longer in the position of "asking" - because you are "telling".
You are demonstrating your boundaries, & letting him know what is unacceptable, without engaging in endless dialogue in which he keeps manipulating you.
You mentioned feeling over a barrel because he still contributes to bills.
So he damn well should.
Don't allow him to use this as a lever to control you with.
If he threatens to withhold it, tell him that it is unreasonable to punish you by refusing to pay for his son, & that if he decides to opt out of paying, that you will take it up with the CMS. Explain that unless he pays willingly, the CMS have the power to take it directly from him via his employer's PAYE system.
The more you assert yourself, the less power he will have over you.
You might find this book very helpful as you go through that process -
www.amazon.co.uk/Woman-Your-Own-Right-Assertiveness/dp/0704334208