It’s a long game and it’s a different game from normal life - often counter intuitive to our initial reactions.
No doubt this week he will have a grand old time as the heat from your end has dissipated so GF will be calm - and manipulative creepy GF mother will be flapping around him to keep her new carer hooked. Expect him to be content - temporarily - don’t be disheartened.
But if you can compartmentalise your RS with him it will help. EVERYONE needs to back off and take the focus of their RS and his acting out - including his GPs. Currently he is emotionally hyper and disregulated by the tug of war - so he can’t think or feel straight because he is tangled up in the trauma between you as well as the trauma bond created between them. He is being pulled all over the shop.
Know that you have done enough nudging, prodding, giving info on abusive RS and coercive control etc but right now the hyped emotional environment is preventing that info to settle, to be absorbed and to be considered objectively.
Only aim now is to get him into calm a emotional state - so that in his own time this information will settle and allow his true repressed emotions to be objectively considered and expressed. He then can’t continue to displace that anger and confusion into you if you have dropped the rope in that part of his life.
Less words - more actions - all v small incrementally steps over the next 6 months. Even when you aren’t talking - he needs to not sense your stress either through your body language or actions. Get back to big fun extended family and friend stuff that he won’t want to miss out on - always invite her - most likely she won’t turn up and if she does he will see how she ruins all the fun. Don’t be the distraction, don’t get in her way - give her the whole stage to herself.