DS2 (4) has always been stubborn / argumentative in nature. When he was 2/3 years old we assumed he'd grow out of it. But over the past year or so he has actually become worse. He is now nearly 5 and constantly pushes back on even very simple and politely-put requests - to brush his teeth, put his shoes on, turn off the TV etc etc. He is a terrible loser and can't bear being told 'no' to anything and can't listen to reason or compromise. These situations quickly escalate into bad tantrums - kicking, screaming, growling, calling us names. We try to put him in his room; he screams and bangs the door with whatever hard objects he can find. Eventually he will calm down - but then the whole cycle just starts again the next time something goes wrong.
I am honestly at a loss as to what to do. This is affecting our marriage, home life, his brother's life and our work. I am exhausted from the constant battling. DH's view is that he needs firmer boundaries and more consistent enforcement i.e. putting him in his room if he crosses certain lines, making him apologise etc but I am not convinced, it just makes each situation escalate hugely and I don't think it prevents it next time.
I've read the Explosive Child book but DS2 doesn't really engage in the kind of problem solving he suggests - too young maybe. He is very intelligent (early reader) and can be absolutely loving and charming; he behaves pretty much perfectly at school. He appears to make friends and communicate fairly easily and has no obvious autistic type traits.
I'm getting desperate. I would love any advice anyone could give. I've also been wondering if we need a parenting coach, especially as DH and I disagree on how to deal with is, any recommendations would be great (we are London based).