Behaviour from 13 yo is unacceptable

[Nicknamegoeshere]

I'm 50/50 parenting with my narc ex-husband (court ordered) and have been for seven years. We're going through the court process yet again as he wants even more custody (revenge tactic). No money now to buy a house, still renting as spent all on solicitor. My ex remains in the huge family home.
My eldest is now 13 and ASD. The pattern of behaviour is he's always very abusive towards me when I collect him from
his dad's. Says he wants to stay there and calls me a fucking bitch, a whore etc. Ex just stands at the door and says nothing.
Within literally hours of coming home son is lovely again. Polite, wants to be involved in family life, plays and interacts with his half sister etc.
But the night he is due to return to my ex he turns abusive again. I've been called every name under the sun again tonight and been told to fuck off again and again.
My 10 yo is ubserstandably so upset when his brother gets like this. He can't sleep and constantly seeks reassurance from me.
We've had so many professional involved.
Why can't they see what my ex is doing to us? Why won't they stop it?

First of all, what is being done to retrieve your share of the family home?

Also, could you look at counselling for your son and yourself and younger child?

Your DS with ASD certainly needs some counselling. Such a change in behaviour that coincides with contact with his father can indicate that he is being abused by the father. ASD children are especially vulnerable to verbal and emotional abuse. It’s almost like he is a hostage who has to mimic his father’s behaviour towards you in order to survive.
You need to get him help and consider supervised contact order or no contact with father (especially if the father actually has narcissistic personality disorder as hinted from your OP where you have said he is that).

That sounds like an absolutely horrific situation for you, I'm not sure I can offer much advice but I do share your disappointment at the response from services that are meant to be looking out for you all.
Are there any local organisations you could contact for support perhaps? Is your son at the same GP as you still? I'd gladly have a search around if you'd post your area or message privately x

Thank you so much all. His father is taking me to court yet again, asking for even more custody. I know it's to punish me.
Re the family home, I got a settlement so he could stay in it but nowhere near enough to buy a place of our own. He changed the locks within hours of me leaving with the kids for our safety.
Courts are saying we have to have family therapy but again this must be paid for. This means the deposit I had kept for housing is going.
Also mediation but I am terrified. How can I mediate with a monster? Do I forget the times he used to take my money out of my purse so I couldn't buy food? The months I had to sleep on the floor? The judge seems to think so as he won't look at historical evidence.
My son won't access any MH support as it's all "my fault."
Even seven years on they are days when I really wish I hadn't left my ex-husband and just tried to tolerate the abuse.