How to help an angry child?

At the moment I don't have the answer and it is not due to the lack of asking the question. I have asked our social worker, I have asked the school and I have sought advise from family and friends but still the answer to the question is beyond my reach. How do I help my angry little boy? I am pretty certain that his anger is rooted in a couple of things - his insecurities about having to move on and jealousy of his sister being the 2 most easily coming to mind.

The first is a case of time and constant reassurance. I tell both children every night at bed time that I love them, that I will always love them and that I will see them tomorrow. I tell them when I leave them at school that I love them, that I will always love them and that I will see them when I get home. I have asked him if he is scared that he will go somewhere else, he says not. I asked him if he was happy living with us, he says he is. I always assure him that he will always have a home with us. But he often turns on me, in anger, and tells me that 'when I am a grown up and I live in my own house . . . '

The second is much harder. I don't want to keep them apart all the time, they have this at school and pre school although in September they will be back to being in the same setting just different classes. To be honest they are as bad as each other but he gets a lot angrier. They squabble over toys, they both want what the other has and they are usually more interested in what the other has got/ is doing. I know that this can be seen as normal sibling behaviour but sometimes it feels like more. I also have to recognise that when he is angry she is more often than not his target. And he lashes out physically.

When we talked to school they were brilliant, they offered him assessments and additional support. I am hoping that it helps him. I am also hoping that they can offer us some advice to allow us to help and support him.

I think that there are 2 things that will help above everything else.
Time.
Us.
We are going nowhere and time goes past every minute of every day.

Hopefully it will help.