First of all, the Chantix should have had him not smoking by now if he's been taking it like he's supposed to for a month. It can take up to 3 months, but by now, he should be smoke free. Sounds like he's not really ready to quit. No drug can make you READY to quit. As far as the moodiness goes, it can really make you feel a bit nutty.
Is he having extremely vivid dreams at night? Chantix can cause very vivid dreams that can disturb his sleep, which can make for a very cranky person. I had crazy dreams on it. They weren't nightmares, necessarily, but just wild. Also, a girlfriend of mine took it and her husband said she went into a state of depression. She snapped at everyone in the house and would only get out of bed to go to work, then she would come home and put her sweats on and go back to bed. She is a very social person and likes to go out with friends, but when she was on Chantix, she barely functioned.
Remember that it is a drug, and every drug, even Tylenol, affects people differently. I would maybe go see your doctor and talk to him about the side effects or you can even go talk to your local pharmacist. Hang in there! If he quits smoking, you'll have him around for a lot longer. That might be enough incentive to put up with the moodiness for a while.