Bad mum? vs struggling pre-teen

Hi all,
I would love some advice on the best way to support my 13 yr old son (asd, adhd) right now. I share custody with his father.
I have recently come out of an extremely toxic relationship, and as much as I tried to protect my kids from the impact I know it has definitely affected him. He doesn’t bond with people easily and he not only bonded with my ex, he loved him. Since my ex moved out my sons behaviour has gone downhill, getting into fights and trouble at school (a lot of it due to being bullied). Every time I try to talk to him about his behaviour he says that I hate him. Now I’m being told that I work too much and am not home enough, he micromanages everything I do and if I am not 100% available for the kids (to the point of clearly neglecting myself by not sleeping and eating) he gets angry or incessantly questions me and I’m treated like I’m selfish, but I honestly don’t do anything for myself when my kids are with me, it’s all about them. He also says I’m not letting him grow up, but this is after he does something that I didn’t even let his older brother do until he was older. He honestly just doesn’t care about anything anyone says, does or wants right now and just wants to grow up as quickly as he can, which scares me on a whole new level.
I can’t work less right now and am doing my best to give my kids everything I can, but it never feels like enough for him especially.

He does see a therapist but I’ve struggled getting time off work to take him, he has now agreed to allow a support worker to take him and I’ll come along when I can get the time off.

He seems so lost and I am so worried about him 😞 I know this is my fault for bringing my ex into their lives in the first place, for not leaving sooner. I am doing everything I can to make up for this but I am becoming so worried about how quickly he has declined. I honestly think he is depressed and worry constantly that every decision I make- even down to not letting his friends stay over while I’m not home this weekend- will push him further away.

I worry everyday that I’ll get a call from the school and find out that he has been hurt again, that he has mucked up again.. I worry non stop and it is making me miserable which then makes him and his siblings even more overwhelmed (I try to hide it and deal with my stuff away from them because I don’t want to create more trauma for them). What if I’m too hard or not hard enough?

He is lost, I am lost.. any advice on where to go from here or personal experiences would be amazing! Have I lost my sons trust and set him down a shitty path forever now? Is it possible to stop feeling like such a shitty parent? I feel like I’m constantly failing them no matter how hard I try not to 😔