The study in question for second hand smoke has been exposed, it's not necessarily false, but it's definitiveness has been shattered. I don't remember when but it was about five years ago. Still, there is no immediate danger to the public from secondhand smoke, remember, the danger must be clear and present, both requirements must be met and demonstrable, also, it must be something that poses an immediate threat. So in the private smoking ban example, basically a governing body is telling a private owner they are a partner in policy even though they contribute nothing to the business.
I am not a fan of the "community standards" argument. While the concept has been upheld by the courts it is easy to abuse. I've seen communities, including my own say a majority of people don't want something, but I live in a city of 140k+, when four people can't decide on pizza toppings I find it hard to believe that a community of more than 2 people are going to have standards that are so close as to pass a law against someone else's pursuit of happiness.
Taxes can be theft if they are not representative, punitive, or excessive.
Again, the test for necessary and proper is simple and complex. It's simple enough to make a case that something is necessary, the complexity comes from scrutiny. For instance, a smoking ban, convenience and comfort of a singular individual or even a majority of such isn't a compelling interest to trump private property rights, therefore it would reason that unless smoke can definitively kill someone in that moment directly, then that would be the only starting point that would be constitutionally acceptable. Basically every right has a limit, and every argument for expansion of limits has a counter, but to limit a right or priveledge should require intense effort.
Simple, it's not our business. People should have all the freedom in the world to make mistakes, the difference comes from someone maliciously causing harm, to play off of your financial example. I am in the financial field and eventually plan to expand my business lines, there is fraud, ethical behavior, and honest mistakes. We insure for honest mistakes, but I have seen some fraud and what it does to people's finances, it's not pretty. So laws protecting people from fraud and exploitation, sure, but where's the line when no malice is present? Moreover, where is the line when much of what looks like abuse is actually financially necessary because of government presenting influence past what it should?