OP, you’re twisting yourself up in knots here trying to find ways of justifying the way he treats you. There’s no maybe he shouldn’t have behaved like that, he shouldn’t be speaking to you like that, ever. You say he made you feel like a little child, but would you call a little child thick and a stupid bitch?
It’s very clear that you have been forced to change the way you act so as not to tip off his temper. Ok nobody acts perfectly at all times, and it might be that you did need to curb your tongue a bit, I don’t know, but it hasn’t worked, has it? You’ve said yourself that he blows up over increasingly smaller things, so what does this tell you? You have made efforts to curb the excesses of your behaviour, whether they were really excessive I don’t know, probably not particularly, but instead of him trying to do the same, he has increased his.
I also think you need to stop telling yourself porkies about why you feel uncomfortable about telling your mum. You know she grew up in an environment like the one your DC are growing up in and that it’s damaged her, and you also know it’s not because you don’t want to upset her that you don’t like telling her. You don’t like telling her because you know that what she’s telling you is the truth, that this behaviour isn’t acceptable from your husband and that it will have a massively negative impact on both you and your DC.
As for your H: notice it’s not his stuff he throws and breaks, and if he’s such a fucking amazing boiler guy why was he leaving the pressure to flatline at zero? Everybody knows you shouldn’t do that, and that it is as likely to knacker your boiler as over pressurising. If he’s such a genius he should know that, the twat.
I think you could try couples counselling but it’s not advised if there is abuse in the relationship, which there clearly is. I think you’d be better spending the time and money having counselling by yourself to drill down into the reasons why you are willing to accept this behaviour, and why you think it’s ok for your DC to be exposed to it. You’re ignoring your mother, who has direct experience of growing up in a household where abuse is present and I think that would be a much more worthy avenue of exploration than trying to make your H desist in behaviour that he’s clearly choosing to engage in. The fact that he’s choosing to engage in this behaviour means that it has some benefit for him, and he clearly thinks these befefits are worth it, so you’d be wasting time and energy trying to get him to change. Instead you need to look at how you need to change, because at the end of the day that’s the only thing you have any control over.