I understand. My 12 yr old has had a similar morning because he's worried about the summer holidays.
Things we've done that have made a difference (if you're interested!)
5 point scale - helped to spot escalating behaviour before it's too late (Google The incredible 5 point scale, there are scales to print out on the website, or he can make up his own scale so it's more personalised. Basically 1 = fine up to 5 = meltdown. By 4 it's too late, batten down the hatches, meltdown will happen! It's not perfect, but it does help you and him to learn to spot how he's feeling, and to learn how to de-escalate things whilst you can. We lived in fear most of the time, this has given us some control back.
Sensory and calming strategies - if the tablet was helping him to feel calm at a time of heightened anxiety, I probably would have left him to it. I know that flies against "normal" parenting techniques, but I know myself (i am autistic too), feeling anxious is horrible and having a distraction taken away is very distressing.
Has he had an OT assessment? We found strategies from an OT were fantastic, far more helpful than anything camhs suggested. Things like jumping on a trampoline, pulling himself up on a door bar, chewing gum, press ups, using a weighted blanket, although it's very personalised. There's a book from West Midlands Autism called Sensory Profile which is very cheap and excellent, and helps you to build up a sensory diet for your son.
The book The Explosive Child is brilliant, and helps you both to learn to collaborate and find solutions together, you might find this very helpful. I think you can get these quite cheaply second hand on Amazon.
My son was suicidal from 6, it's difficult, but often it's a way to explain how bad he's feeling as it's difficult to identify and name emotions without being extreme. It's still worrying though, I know.
Sorry if you weren't wanting advice. Feel free to ignore!
I can completely relate to your post though, ds doesn't have a bedroom door any more as he destroyed it, we also have random holes in our walls which we don't want to fix until we know things are more settled. We now HE our son which is much better for him, but not great for me, so we're trying to apply for an EHCP to get something else worked out.
Does he have any involvement with autism outreach at school? (Called different things in different areas). School can refer him and someone will come in and help to put into place some strategies that help.
We try to have a holiday timetable that ds has input into, it helps him to feel in control and helps us all to have some sort of predictable routine that we can see, we tend to have daily lists which we write as a family so we know what everyone is doing and when.