I read your post earlier, but just now I read it and something jumped out at me. When you mentioned changing your name. I suspect he feels abandoned by you since you moved a man into your (and therefore his) life, he feels like he's not your "main person" anymore. And with you having a different name, now he feels all alone.
He needs to know you are there for him. I try not to give advice, but this time I have advice:
First, you must be sure that all discipline comes from you and not from the new person. Anything else is too much for a child. Be consistant, and just as you were before you married.
Sit with him, just the two of you, and tell him how very much you love him. Remind him that he's your sweet baby and will be even when he's all grown up. Try to have plenty of alone time with him, even if it's like a "date night". Be very present with his school, homework, etc so he will know you are in his corner.
Tell him that you will not accept any bad talk to you or anyone. Let him know that he is expected to show better character than that because he is a good person. Help him find words for his frustration. If he yells that you're just stupid, calmly tell him that you know you aren't, and ask him what has frustrated him. If he can't find what it is help him along. A few times with a therapist might help here.
Have your new husband start teaching him "man things": filling up the car with gas (if he's big enough), opening the door for you, pulling out your chair and seating you, how to dress well, etc.... all the things we forget to teach our little boys. Also, suggest that they do some "guy stuff" together: throwing a ball around, watching his team practice. Let him take him to his music lesson, etc or to a professional sporting event (I don't really know what guys like to do).
Make a point to do family things, all of you together. Make sure he knows that you didn't give him up for your new marriage.
Above all, ensure that you and your new husband are not modeling this undesireable behavior. If he puts you down or yells, that what your son will know to do. As he esteems you and builds you up, that's what your son will know what to do.
I wish you well with this.