Hi Lorns
I also just wanted to offer some support my son is the youngest of two and 6 years old.
He sounds very similar and I have had lots of similar types of situations you discribe, especially linked to the computer.
I have to use the timer when he goes on anything like the computer, playstation, gameboy, television, or else I have a real problem getting him off.
He also gets really cross if things go wrong and has been know to hit the computer and throw things through frustration, he also blames others whenever he can, he just does not like getting things wrong.
He has even argued with the teacher at school about spellings, I get the dictionary out, but he still disagrees with me.
It is very hard sometimes, these things are also quite subtle, as on their own, they seem quite small, but put together with all the other small inflexable things that you have to deal with on a daily basis, they can really wear you down.
I must agree with trying to be as positive as you can, it is so easy to end up in a negitive cycle where all you say is don't, don't, don't.
I try and praise as much as I can, for all those little things like saying thank you, turning the light off, helping in any way. It all adds up, but I do often end the day wishing I had done things differently and feeling a bit stressed.
The best thing anyone ever said to me is " try and be a good enough parent" I do feel the pressure of trying to get it right, and often failing.
As for the anger side of things, I don't quite know where that will end up. DS2 was very agressive last year and we had a very difficult time at school. He seems to have calmed down now and is not lashing out at others like he used to. He does still say some very worrying things and he has also threatened us with knives etc.
It can be very hard and you have to just take it one day at a time.