I tell him his behaviour isn’t acceptable. I use distraction “oh i would love it if you help me with chopping the veg” (he loves to be involved). yesterday after this incident, I had got him mowing the lawn because he’s been desperate to do it, seeing it as a grown up thing to do. So I taught him how to start the mower, line up the rows etc. It was all going brilliantly and then my DH went out to have another pop at him.
I take him on long bike rides to get rid of his nervous energy, I do breathing exercises with him. He has counselling at school to build emotional resilience which is where a lot of the backchat comes from. A feeling of low self-worth. I tell him he’s beautiful, thoughtful (he is) and a fount of all knowledge (he loves facts) and pray that one day, it will all be okay. It’s been a painful, long journey. But I do think his behaviour and resilience are improving. He has so much going for him if only...has been the resounding sentence from his teachers throughout his life...I’m trying.
OP I'm not defending your husband. That is not the way to behave towards an 11 year old. But this part of one of your posts does make me think that there is another side to this.
Because you perceive low self esteem and possibly ADHD, you are trying to build him up emotionally. No problem with that. But what you've written suggests that maybe you also go too far the other way. He seems to be rewarded for his bad behaviour because you distract him by suggesting doing the things he likes to do.
He obviously gets a lot of your time and attention. What about his sister? Does she get the same?
He wanted to do the lawn - so you spent a lot of time with him, explaining how to do it and then letting him get on with it. Did you precede it with 'tidy your room and then I'll show you how to mow the lawn'? You praise him for being beautiful, thoughtful and knowledgeable - does he now have the impression that he's the apple of your eye and can do no wrong? You say you tell him his behaviour is unacceptable, but are there consequences or do you move on to do something he wants to do as a 'distraction'? I'm not suggesting you beat him with a stick, but are there actions as well as words?
He needs boundaries. And maybe he's being gobby and chats back because with you he gets away with it. Maybe you let him to compensate for your DH's behaviour, or because you believe that you are doing the right thing to build up his confidence. But there is a middle ground that leaves DS in no doubt that some of his behaviour is unacceptable, and that it won't just be smoothed over or rewarded.