First, 3rd and 6th issue: Use setpos command to drop baloon from a certain height.
2nd issue: use setmass command and see no change in how fast the baloon fall.
4th issue: Place some (air filled) baloons and then drive over them with quadbike and some heavy tracked vehicle. Drive with higher speed (40kph+) and your quadbike will probably flip.
5th issue: Place long row of (water filled) baloons then shot trough them with some low penetration weapon like a pistol.