OP. I’ve been where you are. Your EXH sounds a lot like mine.
we don’t have the ASd but the rest of it is thr same. Child sobbing down the phone etc.
If your EXh has parental responsibility DS can’t legally be removed from his care. But the closer DS gets to 14, the more his views will be taken into account.
I’d say you’ve got a 2 step process here. 1. Holiday: Text DS today and find out how he’s feeling about the hol. Try to reassure, encourage etc, it’s only a week, etc. If he’s adamant he can’t go/ is distressed, he’ll have to tell his dad he can’t go because he is too anxious, and you’ll have to back him explaining that his ASD won’t allow him to go, etc.
then be prepared for the fight but be clear it’s the ASD up that’s the issue. If your EXh is anything like mine, he’ll need something to blame. That will probably he you, but you can deflect some of it through the ASD.
step 2, revisit contact. It isn’t your EXh who has rights, it’s your son. He’s now 9 and has a voice. It’s an awful process to go through, but it will be different now from when he was little.
my DS is 14 now and has no contact with his dad. There is not a thing EXH can do about it. For you, it really is just a question of hanging in there and trying to get through as best you can, with DS needs and wishes at the forefront, for the next 2-3 years.