K.:
It sounds like your child has found out that screaming to the top of his lungs is the best way to "Get his way." Unfortunately, putting the finger in his mouth by either parent is torturous (in my opinion). Here's what I suggest:
Put up a chart of his favorite things such as toys, books, movie, blanket, pillow etc:
Explain to him when he is rude, loud or misbehaving that one item at a time will be taken from him. When you explain it, demonstrate it explicitly with one of his items. Also explain that if his behavior improves, then the item will be returned to him.
More importantly, in the beginning he will scream, but you and the husband must stay strong and firm and IGNORE him when he screams. Eventually, when he sees this does not affect you nor him or the sibling, he will stop.
In sum, make sure that no one in the house screams for any reason and he will model that attitude as well. If you and or the sibling scream at each other on occasion, then he will scream for he has had training from the two of you and if it is the father, he must be told the same thing as well. As a further incentive, print a few signs over the house that reads "NO SCREAMING PERMITTED in the HOME" just to remind everyone. It works in mine.