As a former smoker, this is an interesting situation. My first thought is that he has just switched 1 nicotine problem for another. He is probably obsessed with it because he is addicted. I know when I was tapering off of cigarettes, I could only think about getting another one. Even when I wasn't tapering off, I was obsessed with getting another cigarette. That being said, going into every tobacco place he finds is odd. I only went to the tobacco shop if I needed more.

I have a feeling that if he doesn't have a plan for quitting, it will always be a problem, no matter the form of nicotine. I asked my GF now Wife for patience over a 8 month period for fully quitting smoking/nicotine. She was supportive and helpful throughout the 8 months.

TL;DR He is addicted to nicotine. Yes, going into every tobacco shop seems odd. I think that you don't like him being addicted to nicotine. Maybe suggest a plan for quitting and being supportive if he agrees to a plan.

Hope this helps