I used to have severe FPS problems, but I realized one thing. The graphics settings don't change until you exit the program entirely and restart. Nothing will change even if you reload the game. It took me a few days to figure this out, but now its running fine for me on Medium, and it still has graphics on par with the latest Source engine releases. Default settings are on Medium I believe.
And David, the weapons were meant to be that accurate. Turn on the crosshair ranges to see how far you're firing. You're not getting an accurate pistol shot at 75 to 100 meters. And add to this the fact that you're a survivalist, not military. If you want a bit more accuracy, try grouping your shots into two or three round bursts. Its not more accurate necessarily, but you have a better probability of a hit. And with most pistols, you'll have enough ammo to blindfire as much as you want.