This happened at Fort Myers, Florida. I fly out of there often and frequently have my flight bag searched. Apparently, the harmonica that I keep in my bag "looks like a pistol clip" Clueless A-Holes
The air in the cabin IS NOT recycled. It is a constantly refreshed system. The air flows through the cabin and exits through the outflow valves. It is NOT recycled or recirculated
I hand prop a variety of vintage and homebuilt aircraft on a regular basis. In addition to the many great tips posted here, my practice is ALWAYS hand prop from BEHIND the prop. It simply is safer this way and gives you a greater distance between your lower body & the prop disc. In many aircraft, you can also "chock" the right main with your foot for greater stability. The exception to this technique is when propping a pusher, such as the Vari-Eze I once owned.
There would not be any negative Gs during the descent. Even at 10,000 FPM it would be a steady state drop. The attitude of the nose wouldn't matter either.