Let me answer this bit-by-bit:
Your questions are ridiculous, and have very little to do with the topic. It's never legal to murder someone, under any consequences. I find it silly to equate the negative health effects of smoking to a bullet in the head.
Secondhand smoke is damaging to your long-term health at best and lethal at worst. I deliberately chose a more dramatic analogy, but the comparison is not unreasonable. In my post, I never said the gunshots were fatal; you assumed that. So is it okay if someone walks into a resturant and only fire at your legs or hip, rather than the head? Does causing non-fatal injuries make it okay?
Let me pose a question to you - would you walk into the middle of a shooting range where people are constantly shooting and then blame the gunmen when you get shot? If you walk into a restaraunt that you know allows smoking, you are doing just that - you are taking a risk of your own free will.
A shooting range is an isolated area specifically for shooting, a resturant is not. People should not have to fear for dangers when they walk into a resturant. Nor should they be forced to think about which resturants harbor threats and which do not. The convenience of a few smokers should not rank higher than the lives and convenience of ordinary people.
Even libertarians should agree that government has the responsibility to protect lives and public safety. Individuals should not be allowed to threaten other people's lives, private property or otherwise.
And furthering your logic that smoking is like shooting people, it would be just to forbid people to smoke in their own homes, at least when they have company. Are you fine with people having their habits regulated in their own homes?
If my habits are hurting other people who are in my home, government should protect those people. It is no different from someone abusing their wife and kids in their home, etc. When there is a threat to people's lives, whether it's on private or public propery is irrelevant.
