The structure appears to be something like this: everybody quitting smoking => fewer deaths from cardiovascular disease => money saved in health care. Also, everybody quitting smoking => increased productivity in all industries. Money saved and increased productivity are good things, so everybody quitting smoking is a good thing.
"It has been proven that a smoker who quits smoking can reduce their risk of cardiovascular disease to almost that of someone who has never smoked." - There is evidence of this, though statistical evidence usually falls below being "proven".
"Thus, quitting smoking is beneficial for the quitter." - Beneficial is an evaluative term. Maybe the smoker prefers the enjoyment they get from their cigarettes to the risk of disease. I know people who are aware that eating bacon has health risks but wouldn't dream of giving it up. There is also a potential confounding variable here: the argument has moved from a general statement about the frequency of disease to a particular statement about a smoker. But individual smokers, depending perhaps on genetic factors, might be highly unlikely to develop cardiovascular disease, even if they smoke, so there is no safe inference to the individual case.
"... if every American smoker stopped smoking... this would lead to a saving of $211 billion" - on the face of it this is a complete non-sequitur. Everybody dies of something, so every smoker who quits and doesn't die of cardiovascular disease will die of some other condition and incur the health care costs of that. Without knowing how the costs of smoking-related diseases compare with others, there is no way to know if any money could be saved at all, or even if it would be more costly. Also, people who quit smoking frequently become obese, which carries its own health issues.
"...people quitting smoking would result in a massive surge of productivity" - there would likely be some effect: there would be fewer cigarette breaks and perhaps fewer sick days, but calling it a massive surge sounds like an exaggeration. It would also, of course, put a lot of people out of work in the tobacco industry.
"Thus, every Australian smoker who quits does good both to themselves and to the Australian society as a whole." - there is a kind of fallacy of division here. Even if it can be proved that there is benefit in everyone giving up smoking, it does not follow that there is any benefit in one person doing so. There might be a threshold below which there is no noticeable effect.
Also, speaking generally, it is not safe to argue "X is a good thing, Y leads to X; therefore Y is a good thing." In practice Y might not be the best way to achieve X; it might entail additional risks; it might engender unintended and harmful consequences; it might conflict with other goods, etc.