A day in the life of me and my son...

Today has been a real tough day for me.
Firstly I took my son who has been signed off of school due to now having a chest infection.
There was my first mistake taking him to work with me. After promising he'd be good and that he would stay in the van and do the work books I brought, he did two pages, complained they were to hard ( simple maths add 3 ) and through a hissy fit and stopped off into the van hitting me on the way past.

After that I got called stupid for around 45 mins and when he didn't get a rise out of me he then started kicking and punching me in every place he could reach. I managed to distract him thanks to a college working alongside me but this didn't last for long.

So I left work early due to the people walking by and giving me dirty looks for allowing him to act the way he was ( which I wasn't allowing him at all, I just couldn't stop him).

He seemed to calm down on the way home and fell asleep for 45 mins. I left him to wake up by himself while I sorted out stock.

Homeward bound.

Supper cooked and eaten, bathtime full blown refusal. Left to calm down and he ends up trying to break my knee cap.

How many times do I have to put up with an 8 year old bullying me?
How can I stop him?

What's worse I'd the fact that as he gets older he's only going to get stronger and everytime I ask for help I don't even get a response.

When you ask and ask and ask .....

Looking at my 8 year old he is normal. He's has his outbursts like every child has. But deep down a parent knows when something is wrong.
For 6 long years I've gone to the doctors and asked for them to help, to test, to refer me to someone who could help. For 6 long years I've been knocked back with the same answer " it's your parenting " .
2 years ago I signed up for the Webster Stratton 16 week parenting course to help tweak my parenting.
Now 16 sessions of which I had to take time out of work to attend (this caused a lot of issues, and ended up with me loosing my job due to the course), I found praising Tj continually made him angrier. The course itself and the structure is built for children that do not have anger issues.
Anyway 2 weeks ago I privately hired a physiologist to come and help Tj through his anger. It's amazing the lady sat with us watched Tj and even spoke to him by himself for a while.
Whilst here she watched and observed. And by the end of the session she agreed there was something wrong. She suggested he had R.A.D and possibly a slight form of autism.

Why in 6 years has it taken so long for someone to agree there is something wrong.
Last week I managed to get a doctor's appointment gave him the paper and he looked at me blankly then asked what I'd like him to do. The words "help me get help for him" came out of my mouth and again  the doctor looked blankly and said all he could do was refer me.
After all these years of not being helped I've gotten used to the daily abuse from my child. Bruised stomach, arms, daily temper tantrums and slammings of doors.
But what happens as he gets older?
I can handle my own.
My question to anyone that reads this rant is..... what happens when the abuse turns to someone else? 
When he's older and he stabs somebody ( yes maybe over dramatic but it could happen). When someone blames me for his wild behaviour.

What else can I do to help him but keep asking for help and keep getting denied.

What else can I do?