I mean this very kindly OP, but this is a truly awful dynamic for your children to witness.
He is a petty whiney bully, muttering and huffing....so awful.
Then you are discussing this with your children instead of challenging the behaviour.
This is involving them in the dynamics of your marriage which is so emotionally damaging for them.
He is truly awful but you are wrong too.
You have allowed this awful behaviour to go unchecked for years and years.
You need to have a chat with him away from the children completely, where you spell it out to him.
I think he needs the shock therapy of being asked to leave the home.
His petty bullying is emotionally abusive and you have realised that it is so damaging for the children and it has changed your feelings for him.
Tell him that you do not see a future with his emotionally abusive behaviour.
He is one of those truly odious street angels/house terrorist husbands that bullys everyone in the family with his sour temper.
Your poor poor children.
You need to own this and stop accepting this.
Your children will judge you very harshly for allowing this to occur and involving them in it.
I really hope you find the strength to do right by your children before its too late.
They will be out the door the first chance the get, and who would blame them.