Advisor suggesting my marriage may cause problems in Postdoc position search I am currently looking for postdoctoral positions, and am considering applying overseas (in US right now). My advisor has expressed his opinion that I can not be successful in an overseas position because my wife won't want to move there and will cause trouble. She doesn't like to move, but has realized that it's necessary, even if it's to a foreign country.

To help in my job search, my advisor has arranged for mock interviews with other faculty members in the department. He has provided a list of questions to prepare for, including "How will your wife like living in INSERT CITY HERE?"

I'm not a lawyer, so I don't precisely what section of the law bans questions about marital status, but I know it's outlawed. Even in an academic environment, a professor hiring a postdoc sure seems to fit into the definition of an employer or supervisor, given that he has the authority to hire, fire, or otherwise direct job responsibilities. 

I don't think it's appropriate for him to criticize my personal life, and I have done my best to keep it from interfering with my work. I am mad that he might use my marital issues to sabotage potential job offers. What is the best way to respond to his behavior, and how should I prepare for any potential problems it might cause?

By sabotage, I think he might give negative recommendations. He has told me that if someone asks him for a letter of recommendation about me that he might have to tell them that my personal issues will interfere with my ability to function in the lab. Because this statement happened in the middle of a discussion about how he doesn't think my wife can adjust, the only way I can interpret "personal issues" is "marriage".
By suggesting that you prepare for questions about how your wife will like living in a new place, it seems to me that this advisor is actually trying to help you in your job search, not sabotage you. Even if you only interview in countries where this question is illegal, people who interview you may ask the question anyway (perhaps out of ignorance of the law), in which case it's usually best to answer. And even if they don't ask that particular question, the issue may come up as a result of other questions. I could be wrong (you know him better than I do), but if your advisor wanted to sabotage you, he wouldn't be going to the trouble of arranging mock interviews and confronting this issue head-on.

The letter of recommendation seems to me to be the more critical issue here. I think it depends on how your advisor became aware of your family issues. If these family issues have affected your work, then your advisor may feel he should mention it in the LOR.