I'm aware that this is my second thread in two days about by kids
but after a terrible morning with the other one I am a little despairing about my parenting skills. 
He is the middle ds and can be the most mischievous, funny and helpful little companion. Obviously we adore him, but he has become more and more challenging since ds3 was born 18 months ago.
Firstly the positives. Heis helpful, companionable, loving and cheeky. He loves having tasks and really rises to challenges. He has lots of special time with me and his dad and is happiest outdoors helping his grandad with gardening - building bonfires, cleaning out chickens etc.
However - he has absolutely no respect for authority, fights incessantly withds1 (nasty point scoring, trying to separate ds1 from his friends when they come to play and acquire them for himself) has no fear of consequences etc.
He already displays scary risk-taking behaviour (says he can't wait to ride a motorbike and join the army) and doesn't give a shit about consequences. His nursery teacher finds him rude and cheeky a lot of the time.
This morning was a particular low point. He refused to get dressed (he will only wear 2 outfits) and his tantrum was epic. He then attacked his brother (who has scarring on his face from ds2 scratching) and tripped up his dad. He ran down the road and had to. Be manhandled into the car for his lift. This is not an isolated experience. All the while he has an incredibly annoying and defiant laugh
.
Often eventually his facade of bravado will crumble, his lip will wobble and the sweet 5 year old will very remorseful, but this is when the fights have been appalling.
Last weekend we tried lovebombing him but he wore a paper crown and behaved like a dictator. And it has had no longer term effect on his behaviour.
I know life is tough - grid 20 months younger than ds2 but bright and able and 2 academic years behind. He is bored at nursery, snapping at his big brother's heels and disenfranchised by his baby brother. I'm at my wits end - I don't want him becoming completely unmanageable- help please. 