There are volumes of cases that are at odds with your analysis. I could not possibly do justice to the topic in one post. The Courts, however, make a great distinction between conduct that transpires in one's home, as opposed to conduct in a host of other venues. Thus, one is most secure from search and seizure in one's home. One is less free in one's car.
With respect to security checks at airports, the issue was long ago settled. If you do not want to be searched, don't go to the airport. But make no mistake about it, the Courts will give no comfort to someone using a fourth Amendment argument to defeat a security check at an airport. There is no Constitutional right to fly.
Show me one in which the Court upheld a non-administrative search or seizure without probable cause or reasonable suspicion.
You're also not quite correct about security checks. It's boarding planes, not entering airports.
Irrelevant. There is no constitutional right to walk on the sidewalk, but you are protected from being searched there by the 4th amendment.