Battery issues
What a neutral safety switch?
The car looks like it has been wired for aftermatket radio and sub but there's none in the car...
Both interstate batterys have survived like a week each. At first headlights would dim then the car won't start
Neutral safety won't cause what is happening here. That is the switch that only allows the car to start (if auto) in park or neutral
OK---if the mechanic has "cleared" your starter and alternator the most probable thing wrong is
SOMETHING DRAINING THE BATTERY
As I said earlier, unhook the negative (ground) battery cable. Make sure EVERYTHING in the car is off, and once again, use your HEAD. Make sure there is no trunk lite, map lite, etc, on, and put a test lamp in series between the ground cable and battery.
IT SHOULD NOT LIGHT. If it does, either you left something on in the car, or you have a DRAIN.
If you have no test lamp, get the cable connection in the dark (garage or near dark) and look for a small spark as you hook/ unhook/ try it again, hook/ unhook. A small spark also indicates a drain going on
If this is so indicated, remove fuses one at a time and see if it "goes away." If removing all fuses does not remove drain indication, I'd guess from the sound of things that it's time to find a good electrical mechanic.