Take steel or aluminum alloy, machine it to the shape of the frame, do the same with the slide. Take a length of steel rod, bore a hole thru it in .380 caliber, and rifle the inside, and cut a chamber for the cartridge. Bend steel wire to form the springs, and sheet metal to form the magazine. Using a lathe to turn steel to make a firing pin, then harden and temper the steel. Add screws and pins, and your gun is ready to be assembled.
380 auto. Many good brands of ammo out there.
Try want ads, gun shows, gun shops.
Russian made
2mm in case length.
100-1000 depending on exactly what you want/have.
You don't define what "better" means to you. Price? Size?
Near the firing pin
25-75 USD
Best left to a gunsmith
$75-$125, depending on model and condition.
The .380 automatic cannot shoot 9mm Parabellum ammo.
There are several .380 handguns made by several manufacturers, and thus there are several designs and consequentially, several different takedown procedures. You would need to specify what make and model of .380 handgun you have in order for this question to be answered.