I lived with a smoker for several years, watched him try to quit many times and ultimately watched him die right in front of me because of his smoking. I am as antismoking as you can get. So OP no, I don't think you overreacted.
I completely disagree with this. When you have a partner what you do has a direct impact on that person. When my partner died I was devastated. I couldn't even have any type of pure grief because while I was weeping and brokenhearted I was also incredibly angry at him for dying so young and needlessly because of his addiction.
Personally I would never marry a smoker. Smoking isn't just one small aspect of a relationship. Once you watch a smoker get up in the middle of the night to go get cigarettes because he knows he won't be able to have his wakeup smoke, you know that smoking is a central part of a smoker's life and it will have an impact on you.
OP, one of the lessons I learned from my experience is to have your eyes wide open. If you do get married then you make sure he has a good life insurance policy because you may very well need it someday.