One, Not a problem, it was intentional. It's for diassasembaly perposes. And yes, some guns have the firing pin out the back. Look at the Mosin-Nagant, Karbrainer98K, and Springfield M1903.
Second, it's like the KAR98, Your not supposed to push it forward after the last shot. It locks the bolt backwards. Not a problem.
Third, I've noticed that. That is a problem that CAN'T be fixed without fucking the gun up.
I know that, but it sinks TOO LOW. It practiclly touches the ground.
You dont get what I mean, Make a square, change the density to the weight of a car, then cut the square up to make the parts you need. Just make sure the square you use is REALLY BIG to make sure you have enough space to cut out all of the parts. If you still don't understand, I'll make a YouTube video about it.
Scratch that, It actually touches the ground some time. If a car in real life tilts that far when braking and accelerating, your suspension is shit, or you have some SERIOUS power in that car. Take note, this is constructive critisism, I'm not trying to be a dick about it.