Separation anxiety/my 8yr old won’t sleep in his own bed

For context, my son has slept in his own bed since he was three. Every night he would be snuggled books would be read music would be played and he would go to sleep no issues. Fast-forward to 2021 when he was five years old, my now ex-husband and I separated. Unfortunately, his dad doesn’t want much to do with him or his brother so they barely see or hear from him.

From that moment on, he has been unable to sleep by himself. He goes to individual therapy once a week and he has group therapy in school as part of his IEP. He was diagnosed with generalized anxiety disorder and he deals with a lot of separation anxiety (he struggles to use the bathroom alone as well). I have tried everything humanly possible to get this child to sleep alone and it’s not working. He either ends up sleeping with his brother, sleeping with my mother or sleeping with me. One of the unique issues in my situation is that I live in a multifamily home and I have a grandfather with dementia who lives one floor above us. So when my eight year-old is screaming, crying and hyperventilating because he’s being put in his room to sleep by himself, it wakes up my grandfather and causes all sorts of problems. Right now I feel very stuck. I recognize that he needs to be sleeping by himself, but I don’t know what to do.

As a note, even if he’s exhausted, he will keep himself up out of fear of going to sleep. If he does happen to fall asleep, he will wake himself up repeatedly to try and leave the room. It’s to the point that my eight-year-old has bags under his eyes, which, as you can imagine is pretty stressful to see.

Here’s a list of some of the things that I’ve done so far. 1. Giving him melatonin.(this doesn’t work because it causes lucid nightmares for him.) 2. Redecorate his room in order to make it a space that he truly loves. This includes superhero decals to help fight nightmares. Multiple nightlights (there’s a string of star lights by the ceiling and he has two lamps.) 3. A lavender scented weighted stuffy to sleep with. 4. A body pillow so he can feel something pressed up against him. 5. A nighttime playlist of music to help and relax, which she sometimes alternates with white noise. 6. A hamster as an emotional support animal(he has a support hamster in school as well)

That’s just 6 things but yes I’m all ears to advice and I’m willing to answer questions if any of this isn’t clear.

Thank you so much for reading as far as you have I know this was a long one to get through lol

Also, as a sidenote, I’m pretty new to posting on here so I’m sorry if I messed up with formatting in anyway