@PurpleLampShades I’ve been reading your posts and lots (but not all) replies from others, but this is first comment from me, so sorry it might be lengthy.
I don’t always post unless I have a thought that no one else has already suggested but sometimes it’s good to post so that an OP can see lots of people agree with an idea (like a majority vote).
First, I’m sorry this has happened and want to reassure you I think you’re a fantastic mum and haven’t done anything wrong here.
Very difficult situation and I think you’ve been incredibly strong throughout.
You’ve had some great advice and support on here (especially from @stillvicarinatutu and @CloseYourEyesAndSee and @boomoohoo ) but also (imo) some bad or unhelpful suggestions. Most of us can only offer opinions, however well-meaning, so well done on navigating through the best ones and deciding which to follow. I’m finally jumping in as I have some experience of this - not the same as yours, but similar - from both the child perspective AND the parents (2 different situations).
Very happy to DM you more detail - might help but I don’t want to overwhelm you. Send me a DM if you want?
A few observations
You obviously DO have good relationship with DS, he must still love you loads - proved by him staying in touch (despite not often).
I do think he probably sent that text at 2:30am and got your birthday things without her knowing. Very telling that he asked you not to text back saying thanks.
She is obviously heavily influencing him but has not succeeded in getting him to cut you out altogether so be encouraged by that.
The meal was also a positive sign - even if it was for the benefit of SWs to ‘look good’ - you did a great summary of that showing lots of signs of an unhealthy controlling and coercive relationship that hopefully will have been useful for the SW team.
My advice/suggestions
You will need to meet with him and discuss a few things, obviously without her would be best but if they insist she could be there. Hopefully he/they will agree because he wants access to more money - I have some suggestions on how to handle it, but might run out of time so for now 3 practical points:-
1/ Child benefit - Since he is no longer living with you and therefore you are technically not supposed to be claiming it anyway - I think she should claim for Child Benefit, if that’s possible (? I haven’t looked into it, guessing you don’t need to be a parent or guardian?)
Do not just transfer the money value over to him.
This will reinforce the fact that he is officially still underage and needs adults to act on his behalf.
You will look good for coming up with this suggestion and it implies you are starting to accept him living with her. Don’t forget you can always change it back when he comes home.
2/ support for estranged students - do not mention this.
If he doesn’t know about it already, you do not want to put the idea in his head that you are in any way estranged, or give him independent access to additional funds.
3/ Regarding him asking for an increase in trust fund allowance - I do not agree with other posters saying that this is enabling him to stay with her.
I’m very glad that his dad didn’t give him control over the capital until he is 25!
Are you the only Trustee?
Is it solely your decision on how much he gets each month?
Or is another family member or solicitor also involved, and how much detail is DS aware of around the details of the trust restrictions?
I ask these questions because I have a suggestion… when you have had a chance to chat properly with him about how much he wants (and for what purpose - more on that later) - would it possible to increase his allowance with the proviso that it is conditional upon full attendance at and engagement with college?
And also put a time limit on it, so that the amount would be reviewed again when he graduates/ leaves education.
Basically the next time he has a significant change in life situation, but there is always the possibility it could go back down again. I’m hoping there is a solicitor or someone else involved in the Trust administration that wouldn’t mind playing ‘bad cop’ for this reason.