What strategies do you suggest for dealing with my very mean middle son? His sisters are great kids!
It is vitally important that your husband play a key role in teaching your son to be respectful and courteous to others. How he is taught to behave now as a child will be how he will behave as an adult. If you cannot stand to be around him now and he is not taught differently now, the problem will get worse, not better. Character education is the most important education you can give him because he will make a positive difference to others and himself for the rest of his life, regardless of how much book learning he receives.
Try not to compare him with your daughters, which may make him act out more. Identify tasks and responsibilities that he can take on independently or with adult support that will call on his best efforts. Identify his strengths and positive qualities and acknowledge him for those. Keep your words toward him and about him positive, so he doesn't feel as if he might as well live up to being "awful, mean and rude." Sometimes a child will misbehave if he is not receiving enough positive attention. Consider spending time with him one-on-one and encourage your partner to do the same.