1. clearWeaponCargo unitname
clearMagazineCargo unitname
2. No you can't (100%). The reason for the vehicle turning around when exploding is the same reason you can jump up and down (IRL), physics...
There's a script that makes vehicles turn upside down, but it does it so that you can not use it if player(s) have direct line of sight to it when it turns upside down... It basically creates another vehicle near the used vehicle and forces it to turn upside down, so it's not so pretty to look at...
3.Random 6 will results a floating point between 0.000000 and 6.000000... So, it can be something like 2.758934...
If you want it to be an integer, you can use the command
mod as Macguba said... Basically like this:
_rand = random 6
_rand = _rand - (_rand mod 1)
This returns a random number between 0 and 6...
Of course, if I'm spreading misinformation, please correct me
And no guarantees on any syntaxes