I was hypnotized by my IC as part of my therapy. It was a very good experience for me, but I was not attempting to change any habits but rather to access some buried emotions. I think it worked for me because I completely trusted my IC. I had been seeing her for almost a year at the time.
I am not sure how hypnotizing works to stop smoking. Perhaps planting a desire to stop while also planting negative feelings associated with smoking? To me it kinda sounds like a silver bullet (which is fiction btw).
My BIL had good luck with Chantix. He had smoked for over 30 years and has been smoke free for about 4 years now. Like your H, he tried to quit many times before but was not able to kick the addiction.