I disagree with my friend Iomhaigh, you do not want to be placing telephone calls behind the back of your advisor.
Since you are so well liked go buy your advisor a cup of coffee and talk this over. Express your concern that you want the defense to go smoothly. Ask specifically about the ABD issue. Then if he reassures you that everything is going to be fine, accept that and defend.
Congratulations.
Larryc raises a good point here -- I approach these things this way because our graduate program's rules and regulations were horribly convoluted and making sure that everything that needed to happen actually did happen was our responsibility. (Seriously, without multiple calls to the graduate school's main office to ask about forms, deadlines, getting things certified, etc., none of us would have ever graduated.)
If this it not the ways things operate in your world, then the coffee approach might be a better idea.