If the car seems to idle ok, but stalls when you close the throttle while driving in traffic, this usually means the idle mixture screw is set too lean. Identify the idle mixture screw and with the engine warmed up, screw it out a turn and a half. Then screw it in very slowly and listen for the revs rising slightly and idle getting smoother. Keep screwing it in slowly until the engine starts to stumble. Then screw it back out half a turn. That should be about right. You can try a turn either way to get the sweet spot and smoothest idle.
The smell of petrol at the back can be from perished fuel lines, specially those furry braided hoses. They may look ok but they "sweat" petrol, so you never see a real leak. In bad cases it could be the tank rusted through and getting porous.
Cheers R