What do i do?

Okay I need some help. My husbands son is 6 years old and he runs the house. I don't know what to do. I'm literally at my end. He comes home demanding things and when I try to get him under control he gives me the biggest go to hell look. I'm tired of the disrespect but I don't want to to be the step mom that blows my top all the time. How do some of you handle step kids?