Well, the positive thing about you is that you have decided to quit; and i will suggest you not to smoke again for that is the most important step to prevent the development of cancer.
For lung cancer the most important modifiable risk factor is smoking, and you have stopped it.
Risk is highest among current smokers and lowest among nonsmokers. If you do not smoke for next 20 years, the relative risk will decline greatly.
I will suggest you to read out this very useful and easy to understand article regarding lung cancer prevention;
Now coming to the second part of your question, regarding the vitamin supplements you are taking;
In general these are all very safe and useful supplements, having anti-inflammatory properties as well and can benefit you long term.
However, there are still a number of clinical trials going on to safely conclude that such supplements have a definitive role in cancer prevention or not.
There is no definitive proven role of glucosamine in lung cancer prevention. There are small studies suggesting a link between the two, but further large and significant studies are required to prove this.
Certain dietary modifications, such as switching from high fat diet to low fats, plenty of green vegetables and fruits do have a protective role.
You have taken right steps, and based on this i can confidently say that if you continue with these measures, the chances of developing a cancer will be greatly minimized.
Lastly, an important thing; you should avoid second hand smoke as well.
Here is another useful link;
I hope this clarifies and answers your question.
Kindest Regards ***** ***** luck.