What form of address is used when referring or speaking to a stepfather?

As i understand it, you want to know what this man should be called. If by name, personally, it should be whatever he wants you to call him. Dad, Jack, Hey You, Mr. Jones, Uncle Ted. It really is HIS call, in combination with what you feel comfortable with. If by title, it could be, "Dr. Smith," or Mr. Smith, or Harry, or My Stepfather, or, the man who married mom. * Simple solution, discuss with him what he would prefer and what you would be comfortable with.