I've put my heart and soul into this kid. Why is he like this?

[Bobbiebigbum]

I have a 9 year old. He has a very mild disability (not learning or behavioural). I've put everything into raising him at this point and I am close to breaking. He is constantly winding up his younger brother (aged 5), all he does when he gets up is head straight for YouTube or some other tech. He won't sit at the dinner table more than 5 minutes and he argues every night about bedtime. If I sit him next to his brother at the dinner table he will physically fight with him. He's like a neanderthal. I've done everything I can for him, engaged him in after school clubs from cubs to surfing and football. I would say our relationship is pretty strained now. He's actually making me ill with his stressful behaviour. Any ideas? I'm at my wits end.

You’ve left it late but at 9 he’s still manageable
Get those boundaries in place with obvious consequences
I knew my son was going to be huge so I knew I had to have him being cooperative before he got too big and I couldn’t physically manhandle him. He’s always known exactly what is expected of him and what will happen if he doesn’t do as asked. You need to not get over emotional or they will think they have won. Calm but assertive is the way to go and don’t enter into arguments
He’s 12 and 5ft 8 now with the beginnings of a tache but I can make him behave with a look!
To be fair OP, it is easier with 2 of you in charge (3 if you couldn’t his big sister)