Whoa! Let's start with some basics and work our way through this.
First of all, it's not appropriate to diagnose a child under the age of 5 with ADHD. Much of what looks like the symptoms of that problem in older children is absolutely normal behavior in toddlers and preschoolers. So I wouldn't pin that label on your son yet.
More important, it sounds as if you and your husband have quite different approaches to raising children and could both use some education on child development. Books will help. (In addition to my own books, I strongly recommend Dr. T. Berry Brazelton's.)
But what your situation really calls for is a parenting class. Not only will this provide information about child development and discipline (guidance) techniques, it will help put your concerns into perspective. Talk to your pediatrician or family physician to find out what classes are available in your community. Often a local hospital or community mental health center will have this information as well.
Both your husband and you should take the same class. That way you'll have the same vocabulary and experiences to draw upon when you're trying to help your son.