Big Feelings in Small People.

The last two weeks have been tough, child 4 has been clingy, tantrumy and shouty, well to be honest just plain difficult.
He wants to know what he is doing throughout the day and then will ask over and over again when something is going to happen. For example in the half term holiday we were going to my parents one afternoon to celebrate my youngest nephews birthday. "When are we going to Nannas?" "After lunch" "When are we having lunch?" "After we have had breakfast, got dressed, walked the dog and collected the shopping" - major tantrum - on the floor kicking and screaming "that's TOOOOO LONG!!!!!" Then it's clingy cuddle time, he burys himself into my arms and neck sobbing before he asks "when are we going to Nannas?" And so the spiral of behaviour begins again.
He sits on the sofa, watching TV and will shout and scream until someone goes into to see what he wants - his legs don't work so he can't walk into the kitchen to ask for a wrap or a drink.
If we dare to say no, he will call us "butt heads, poos, stinky heads" then slam doors, throw whatever is close to hand, on Thursday he threw the little table across the living room screaming how much he hated me.
He will demand that I tell his siblings that they have to play with him and when I say no he hates us all.
When they do play he will lose his temper if one of them wins or if they are playing hide and seek he doesn't want to count and seek so will refuse to and then have a tantrum when they won't play with him anymore.
In the playground he will react to rough and tumble that gets out of control, with even greater agression.

I know some of this is a phase, some is half term tribulations - routines have changed and he struggles to cope. But I do worry a little that this is a sign of what could be coming. With that in mind we are trying to come up with strategies to help him.
Being angry is fine, being sad, disappointed or frustrated are all perfectly acceptable feelings but tantrums, agression, violence and rudeness are not, so how do we help our little boy with these massive feelings and how do we help him come up with ways of managing them. He is so little but will be heading to school in September, he will alienate friends and staff if he reacts with excessive anger when life doesn't go his way.

We have found that proactive, close supervision is imperative, if we can step in before a behaviour escalates we can help calm everything down.
 I am using picture explanations of his day and telling him only what he needs to know of our plans. This one is tricky as he will ask what we are doing that day the minute he wakes up.
We are always available for a cuddle, this is by far our quickest way of calming a situation. Although it is often on his terms and only when he is ready.
His siblings are managing really well. They are so good at playing with him but understandably don't want to play with him every minute of the day, although it's hard I am sure this sibling play, rivalry and bickering is so important to his maturing. They love him unconditionally but provide tough but natural consequences when he will not play by the rules. With his dad and I in the background to smooth the way he will learn that taking turns, not cheating and not always being the winner is part of life.
We certainly are not always getting it right but we are working on it, hoping that the foundations we are trying to lay will help him throughout his future.