How long until my step-dog listens to me?

Walk the dog every day, and practice the commands that he knows. Ask your husband to show you how he gives commands and corrections (sit, heel) on the leash. You can also practice in short (formal) sessions at home, and make sure that the dog gets rewarded for good performance and response to your commands. Make it fun for him, and always end on a positive note, with something that he enjoys, like fetch or a toy/bone. Be consistent, and show the dog that you are a strong leader. The more time and effort you put into it, the sooner he'll come around. Congrats on the marriage! Good luck!